前言
- 此类仅包含对集合进行操作或返回集合的静态方法。
- 它包含对集合进行操作的多态算法，“包装器”，它们返回由指定集合支持的新集合，以及其他一些零碎的结局。
- 如果提供给它们的集合或类对象为null，则此类的所有方法均抛出NullPointerException。
- 此类中包含的多态算法文档通常包括对实现的简短描述。
- 此类描述应被视为实现说明，而不是说明书的一部分。
- 只要遵守规范本身，实现者就可以随意替换其他算法。
- （例如，sort使用的算法不必是mergesort，但必须是稳定的。）
- 此类中包含的“破坏性”算法，即修改其操作集合的算法，如果集合不支持适当的突变原语（例如set方法），
- 则将其指定为引发UnsupportedOperationException。
- 如果调用对集合没有影响，则这些算法可能（但不是必需）引发此异常。
- 例如，在已排序的不可修改列表上调用sort方法可能会或可能不会引发UnsupportedOperationException。
源码
package java.util;
public class Collections {
private Collections() {
}
private static final int BINARYSEARCH_THRESHOLD = 5000;
private static final int REVERSE_THRESHOLD = 18;
private static final int SHUFFLE_THRESHOLD = 5;
private static final int FILL_THRESHOLD = 25;
private static final int ROTATE_THRESHOLD = 100;
private static final int COPY_THRESHOLD = 10;
private static final int REPLACEALL_THRESHOLD = 11;
private static final int INDEXOFSUBLIST_THRESHOLD = 35;
/**
* 根据其元素的{@linkplain可比自然排序}将指定列表按升序排序。
* 列表中的所有元素必须实现{@link Comparable}接口。
* 此外，列表中的所有元素都必须相互可比（即，{@code e1.compareTo（e2）}不得为清单）。
* 这样的排序保证是稳定的：相等的元素不会由于排序而重新排序。
* 指定的列表必须是可修改的，但无需调整大小。
*/
@SuppressWarnings("unchecked")
public static <T extends Comparable<? super T>> void sort(List<T> list) {
list.sort(null);
}
/**
* 根据由指定比较器引起的顺序对指定列表进行排序。
* 列表中的所有元素都必须使用指定的比较器进行相互比较（也就是说，对于任何元素{@code e1}和{@code，{@code c.compare（e1，e2）}都不得抛出{@code ClassCastException} e2}）。
* 这样的排序保证是稳定的：相等的元素不会由于排序而重新排序。
*/
@SuppressWarnings({"unchecked", "rawtypes"})
public static <T> void sort(List<T> list, Comparator<? super T> c) {
list.sort(c);
}
/**
* 使用二进制搜索算法在指定列表中搜索指定对象。
* 在进行此调用之前，必须根据其元素的{@linkplain可比自然排序}将列表按升序排序
* （例如，通过{@link
* 如果未排序，则结果不确定。如果列表包含等于指定对象的多个元素，则不能保证将找到哪个元素。
* 此方法在log（n）时间中运行以获取“随机访问”列表（该列表提供了近恒定时间的位置访问）。
* 如果指定的列表未实现{@link RandomAccess}接口并且很大，则此方法将执行基于迭代器的二进制搜索，
* 该搜索执行O（n）链接遍历和O（log n）元素比较。
*/
public static <T>
int binarySearch(List<? extends Comparable<? super T>> list, T key) {
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
return Collections.indexedBinarySearch(list, key);
else
return Collections.iteratorBinarySearch(list, key);
}
private static <T>
int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) {
int low = 0;
int high = list.size()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
Comparable<? super T> midVal = list.get(mid);
int cmp = midVal.compareTo(key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private static <T>
int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
{
int low = 0;
int high = list.size()-1;
ListIterator<? extends Comparable<? super T>> i = list.listIterator();
while (low <= high) {
int mid = (low + high) >>> 1;
Comparable<? super T> midVal = get(i, mid);
int cmp = midVal.compareTo(key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
/**
* 通过重新定位指定列表listIterator从给定列表中获取第i个元素。
*/
private static <T> T get(ListIterator<? extends T> i, int index) {
T obj = null;
int pos = i.nextIndex();
if (pos <= index) {
do {
obj = i.next();
} while (pos++ < index);
} else {
do {
obj = i.previous();
} while (--pos > index);
}
return obj;
}
/**
* 使用二进制搜索算法在指定列表中搜索指定对象。
* 在进行此调用之前，必须根据指定的比较器（如{@link
* 如果未排序，则结果不确定。
* 如果列表包含等于指定对象的多个元素，则不能保证将找到哪个元素。
* 此方法在log（n）时间中运行以获取“随机访问”列表（该列表提供了近恒定时间的位置访问）。
* 如果指定的列表未实现{@link RandomAccess}接口并且很大，
* 则此方法将执行基于迭代器的二进制搜索，该搜索执行O（n）链接遍历和O（log n）元素比较。
*/
@SuppressWarnings("unchecked")
public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
if (c==null)
return binarySearch((List<? extends Comparable<? super T>>) list, key);
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
return Collections.indexedBinarySearch(list, key, c);
else
return Collections.iteratorBinarySearch(list, key, c);
}
private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
int low = 0;
int high = l.size()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
T midVal = l.get(mid);
int cmp = c.compare(midVal, key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
int low = 0;
int high = l.size()-1;
ListIterator<? extends T> i = l.listIterator();
while (low <= high) {
int mid = (low + high) >>> 1;
T midVal = get(i, mid);
int cmp = c.compare(midVal, key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
/**
* list中的元素倒序排列。
*/
@SuppressWarnings({"rawtypes", "unchecked"})
public static void reverse(List<?> list) {
int size = list.size();
if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
swap(list, i, j);
} else {
ListIterator fwd = list.listIterator();
ListIterator rev = list.listIterator(size);
for (int i=0, mid=list.size()>>1; i<mid; i++) {
Object tmp = fwd.next();
fwd.set(rev.previous());
rev.set(tmp);
}
}
}
/**
* 使用默认的随机性源随机排列指定的列表。
* 所有排列发生的可能性几乎相等。
* 在前述描述中使用了“近似”套期，因为默认的随机性源仅是独立选择的比特的无偏源。
* 如果它是随机选择的位的理想来源，则该算法将选择具有完美一致性的排列。
* 此实现从最后一个元素到第二个元素向后遍历列表，将随机选择的元素重复交换到“当前位置”。
* 从列表中从第一个元素到当前位置（包括首尾）的部分中随机选择元素。此方法以线性时间运行。
* 如果指定的列表未实现{@link RandomAccess}接口，并且该列表很大，
* 则此实现将指定的列表转储到数组中，然后再进行混洗，然后将经过改组的数组转储回列表中。
* 这避免了因改组“顺序访问”列表而导致的二次行为。
*/
public static void shuffle(List<?> list) {
Random rnd = r;
if (rnd == null)
r = rnd = new Random(); // harmless race.
shuffle(list, rnd);
}
private static Random r;
@SuppressWarnings({"rawtypes", "unchecked"})
public static void shuffle(List<?> list, Random rnd) {
int size = list.size();
if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
for (int i=size; i>1; i--)
swap(list, i-1, rnd.nextInt(i));
} else {
Object arr[] = list.toArray();
for (int i=size; i>1; i--)
swap(arr, i-1, rnd.nextInt(i));
ListIterator it = list.listIterator();
for (int i=0; i<arr.length; i++) {
it.next();
it.set(arr[i]);
}
}
}
/**
* 在指定列表中的指定位置交换元素。 （如果指定的位置相等，则调用此方法将使列表保持不变。）
*/
@SuppressWarnings({"rawtypes", "unchecked"})
public static void swap(List<?> list, int i, int j) {
final List l = list;
l.set(i, l.set(j, l.get(i)));
}
/**
* Swaps the two specified elements in the specified array.
*/
private static void swap(Object[] arr, int i, int j) {
Object tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
/**
* 将指定列表的所有元素替换为指定元素。时间复杂度是线性的。
*/
public static <T> void fill(List<? super T> list, T obj) {
int size = list.size();
if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
for (int i=0; i<size; i++)
list.set(i, obj);
} else {
ListIterator<? super T> itr = list.listIterator();
for (int i=0; i<size; i++) {
itr.next();
itr.set(obj);
}
}
}
/**
* 将所有元素从一个列表复制到另一个列表。
* 操作后，目标列表中每个复制元素的索引将与源列表中其索引相同。
* 目标列表必须至少与源列表一样长。如果更长，则目标列表中的其余元素不受影响。
* 此方法以线性时间运行。
*/
public static <T> void copy(List<? super T> dest, List<? extends T> src) {
int srcSize = src.size();
if (srcSize > dest.size())
throw new IndexOutOfBoundsException("Source does not fit in dest");
if (srcSize < COPY_THRESHOLD ||
(src instanceof RandomAccess && dest instanceof RandomAccess)) {
for (int i=0; i<srcSize; i++)
dest.set(i, src.get(i));
} else {
ListIterator<? super T> di=dest.listIterator();
ListIterator<? extends T> si=src.listIterator();
for (int i=0; i<srcSize; i++) {
di.next();
di.set(si.next());
}
}
}
/**
* 根据其元素的自然顺序返回给定集合的最小元素。
* 集合中的所有元素必须实现Comparable接口。
* 此外，集合中的所有元素必须相互可比较
* （也就是说，e1.compareTo（e2）不得为集合中的任何元素e1和e2抛出ClassCastException）。
* 此方法遍历整个集合，因此需要的时间与集合的大小成正比。
*/
public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (next.compareTo(candidate) < 0)
candidate = next;
}
return candidate;
}
@SuppressWarnings({"unchecked", "rawtypes"})
public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
if (comp==null)
return (T)min((Collection) coll);
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (comp.compare(next, candidate) < 0)
candidate = next;
}
return candidate;
}
public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (next.compareTo(candidate) > 0)
candidate = next;
}
return candidate;
}
@SuppressWarnings({"unchecked", "rawtypes"})
public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
if (comp==null)
return (T)max((Collection) coll);
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (comp.compare(next, candidate) > 0)
candidate = next;
}
return candidate;
}
/**
* 将指定列表中的元素旋转指定距离。
* 调用此方法后，对于i介于0到list.size（）-1（含）之间的所有值，
* 索引i处的元素将是索引（i-距离）mod list.size（）处的先前元素。
* （此方法对列表的大小没有影响。）
* 例如，假设列表包含[t，a，n，k，s]。调用Collections.rotate（list，1）
* （或Collections.rotate（list，-4））后，
* 列表将包含[s，t，a，n，k]。
* 注意，此方法可以有效地应用于子列表，以在保留剩余元素顺序的同时在列表中移动一个或多个元素。
* 例如，以下成语将索引j处的元素向前移动到位置k（必须大于或等于j）：
* Collections.rotate（list.subList（j，k + 1），-1）;
* 为了使这个具体，假设列表包括[a，b，c，d，e]。
* 要将索引1（b）处的元素向前移动两个位置，请执行以下调用：
* Collections.rotate（l.subList（1，4），-1）;
* 结果列表为[a，c，d，b，e]。要向前移动多个元素，请增加旋转距离的绝对值。
* 要向后移动元素，请使用正的移位距离。
* 如果指定的列表很小或实现了{@link RandomAccess}接口，则此实现将第一个元素交换到它应该去的位置，
* 然后反复将置换的元素交换到它应该去的位置，直到将置换的元素交换到其中。
* 第一个元素。如有必要，在第二个和后续元素上重复此过程，直到完成旋转。
* 如果指定的列表很大并且没有实现RandomAccess接口，
* 则此实现将列表分为两个围绕索引-distance mod size的子列表视图。
* 然后，在每个子列表视图上调用{@link
* 有关这两种算法的更完整说明，请参见乔恩·本特利的《 Programming Pearls》（Addison-Wesley，1986年）的第2.3节。
*
*/
public static void rotate(List<?> list, int distance) {
if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
rotate1(list, distance);
else
rotate2(list, distance);
}
private static <T> void rotate1(List<T> list, int distance) {
int size = list.size();
if (size == 0)
return;
distance = distance % size;
if (distance < 0)
distance += size;
if (distance == 0)
return;
for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
T displaced = list.get(cycleStart);
int i = cycleStart;
do {
i += distance;
if (i >= size)
i -= size;
displaced = list.set(i, displaced);
nMoved ++;
} while (i != cycleStart);
}
}
private static void rotate2(List<?> list, int distance) {
int size = list.size();
if (size == 0)
return;
int mid = -distance % size;
if (mid < 0)
mid += size;
if (mid == 0)
return;
reverse(list.subList(0, mid));
reverse(list.subList(mid, size));
reverse(list);
}
/**
* 将列表中所有出现的一个指定值替换为另一个。
* 更正式地讲，用newVal替换列表中的每个元素e，以便（oldVal == null？e == null：oldVal.equals（e））。
* （此方法对列表的大小没有影响。）
*/
public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
boolean result = false;
int size = list.size();
if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
if (oldVal==null) {
for (int i=0; i<size; i++) {
if (list.get(i)==null) {
list.set(i, newVal);
result = true;
}
}
} else {
for (int i=0; i<size; i++) {
if (oldVal.equals(list.get(i))) {
list.set(i, newVal);
result = true;
}
}
}
} else {
ListIterator<T> itr=list.listIterator();
if (oldVal==null) {
for (int i=0; i<size; i++) {
if (itr.next()==null) {
itr.set(newVal);
result = true;
}
}
} else {
for (int i=0; i<size; i++) {
if (oldVal.equals(itr.next())) {
itr.set(newVal);
result = true;
}
}
}
}
return result;
}
/**
* 返回指定目标列表在指定源列表中第一次出现的起始位置，如果没有出现，则返回-1。
* 更正式地，返回最低索引i，以使{@code source.subList（i，i + target.size（））。equals（target）}；
* 如果没有这样的索引，则返回-1。
* （如果{@code target.size（）> source.size（）}，则返回-1）。
* 此实现使用“蛮力”技术扫描源列表，依次在每个位置查找与目标的匹配项。
*/
public static int indexOfSubList(List<?> source, List<?> target) {
int sourceSize = source.size();
int targetSize = target.size();
int maxCandidate = sourceSize - targetSize;
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
(source instanceof RandomAccess&&target instanceof RandomAccess)) {
nextCand:
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
for (int i=0, j=candidate; i<targetSize; i++, j++)
if (!eq(target.get(i), source.get(j)))
continue nextCand; // Element mismatch, try next cand
return candidate; // All elements of candidate matched target
}
} else { // Iterator version of above algorithm
ListIterator<?> si = source.listIterator();
nextCand:
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
ListIterator<?> ti = target.listIterator();
for (int i=0; i<targetSize; i++) {
if (!eq(ti.next(), si.next())) {
// Back up source iterator to next candidate
for (int j=0; j<i; j++)
si.previous();
continue nextCand;
}
}
return candidate;
}
}
return -1; // No candidate matched the target
}
public static int lastIndexOfSubList(List<?> source, List<?> target) {
int sourceSize = source.size();
int targetSize = target.size();
int maxCandidate = sourceSize - targetSize;
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
source instanceof RandomAccess) { // Index access version
nextCand:
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
for (int i=0, j=candidate; i<targetSize; i++, j++)
if (!eq(target.get(i), source.get(j)))
continue nextCand; // Element mismatch, try next cand
return candidate; // All elements of candidate matched target
}
} else { // Iterator version of above algorithm
if (maxCandidate < 0)
return -1;
ListIterator<?> si = source.listIterator(maxCandidate);
nextCand:
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
ListIterator<?> ti = target.listIterator();
for (int i=0; i<targetSize; i++) {
if (!eq(ti.next(), si.next())) {
if (candidate != 0) {
// Back up source iterator to next candidate
for (int j=0; j<=i+1; j++)
si.previous();
}
continue nextCand;
}
}
return candidate;
}
}
return -1; // No candidate matched the target
}
// Unmodifiable Wrappers
/**
* 返回指定集合的不可修改视图。
* 此方法允许模块为用户提供对内部集合的“只读”访问权限。
* 对返回的集合的查询操作将“读取”到指定的集合，并尝试直接或通过其迭代器修改返回的集合，
* 从而导致UnsupportedOperationException。
* 返回的集合不会将hashCode和equals操作传递到后备集合，
* 而是依赖于Object的equals和hashCode方法。
* 在后备集合是集合或列表的情况下，必须保留这些操作的合同。
* 如果指定的集合是可序列化的，则返回的集合将是可序列化的。
*/
public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
return new UnmodifiableCollection<>(c);
}
/**
* @serial include
*/
static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
private static final long serialVersionUID = 1820017752578914078L;
final Collection<? extends E> c;
UnmodifiableCollection(Collection<? extends E> c) {
if (c==null)
throw new NullPointerException();
this.c = c;
}
public int size() {return c.size();}
public boolean isEmpty() {return c.isEmpty();}
public boolean contains(Object o) {return c.contains(o);}
public Object[] toArray() {return c.toArray();}
public <T> T[] toArray(T[] a) {return c.toArray(a);}
public String toString() {return c.toString();}
public Iterator<E> iterator() {
return new Iterator<E>() {
private final Iterator<? extends E> i = c.iterator();
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
// Use backing collection version
i.forEachRemaining(action);
}
};
}
public boolean add(E e) {
throw new UnsupportedOperationException();
}
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
public boolean containsAll(Collection<?> coll) {
return c.containsAll(coll);
}
public boolean addAll(Collection<? extends E> coll) {
throw new UnsupportedOperationException();
}
public boolean removeAll(Collection<?> coll) {
throw new UnsupportedOperationException();
}
public boolean retainAll(Collection<?> coll) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {
c.forEach(action);
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
throw new UnsupportedOperationException();
}
@SuppressWarnings("unchecked")
@Override
public Spliterator<E> spliterator() {
return (Spliterator<E>)c.spliterator();
}
@SuppressWarnings("unchecked")
@Override
public Stream<E> stream() {
return (Stream<E>)c.stream();
}
@SuppressWarnings("unchecked")
@Override
public Stream<E> parallelStream() {
return (Stream<E>)c.parallelStream();
}
}
public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
return new UnmodifiableSet<>(s);
}
static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
implements Set<E>, Serializable {
private static final long serialVersionUID = -9215047833775013803L;
UnmodifiableSet(Set<? extends E> s) {super(s);}
public boolean equals(Object o) {return o == this || c.equals(o);}
public int hashCode() {return c.hashCode();}
}
public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
return new UnmodifiableSortedSet<>(s);
}
static class UnmodifiableSortedSet<E>
extends UnmodifiableSet<E>
implements SortedSet<E>, Serializable {
private static final long serialVersionUID = -4929149591599911165L;
private final SortedSet<E> ss;
UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
public Comparator<? super E> comparator() {return ss.comparator();}
public SortedSet<E> subSet(E fromElement, E toElement) {
return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
}
public SortedSet<E> headSet(E toElement) {
return new UnmodifiableSortedSet<>(ss.headSet(toElement));
}
public SortedSet<E> tailSet(E fromElement) {
return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
}
public E first() {return ss.first();}
public E last() {return ss.last();}
}
public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
return new UnmodifiableNavigableSet<>(s);
}
static class UnmodifiableNavigableSet<E>
extends UnmodifiableSortedSet<E>
implements NavigableSet<E>, Serializable {
private static final long serialVersionUID = -6027448201786391929L;
/**
* A singleton empty unmodifiable navigable set used for
* {@link
*
* @param <E> type of elements, if there were any, and bounds
*/
private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E>
implements Serializable {
private static final long serialVersionUID = -6291252904449939134L;
public EmptyNavigableSet() {
super(new TreeSet<E>());
}
private Object readResolve() { return EMPTY_NAVIGABLE_SET; }
}
@SuppressWarnings("rawtypes")
private static final NavigableSet<?> EMPTY_NAVIGABLE_SET =
new EmptyNavigableSet<>();
/**
* The instance we are protecting.
*/
private final NavigableSet<E> ns;
UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;}
public E lower(E e) { return ns.lower(e); }
public E floor(E e) { return ns.floor(e); }
public E ceiling(E e) { return ns.ceiling(e); }
public E higher(E e) { return ns.higher(e); }
public E pollFirst() { throw new UnsupportedOperationException(); }
public E pollLast() { throw new UnsupportedOperationException(); }
public NavigableSet<E> descendingSet()
{ return new UnmodifiableNavigableSet<>(ns.descendingSet()); }
public Iterator<E> descendingIterator()
{ return descendingSet().iterator(); }
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
return new UnmodifiableNavigableSet<>(
ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
}
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
return new UnmodifiableNavigableSet<>(
ns.headSet(toElement, inclusive));
}
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
return new UnmodifiableNavigableSet<>(
ns.tailSet(fromElement, inclusive));
}
}
public static <T> List<T> unmodifiableList(List<? extends T> list) {
return (list instanceof RandomAccess ?
new UnmodifiableRandomAccessList<>(list) :
new UnmodifiableList<>(list));
}
static class UnmodifiableList<E> extends UnmodifiableCollection<E>
implements List<E> {
private static final long serialVersionUID = -283967356065247728L;
final List<? extends E> list;
UnmodifiableList(List<? extends E> list) {
super(list);
this.list = list;
}
public boolean equals(Object o) {return o == this || list.equals(o);}
public int hashCode() {return list.hashCode();}
public E get(int index) {return list.get(index);}
public E set(int index, E element) {
throw new UnsupportedOperationException();
}
public void add(int index, E element) {
throw new UnsupportedOperationException();
}
public E remove(int index) {
throw new UnsupportedOperationException();
}
public int indexOf(Object o) {return list.indexOf(o);}
public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
public boolean addAll(int index, Collection<? extends E> c) {
throw new UnsupportedOperationException();
}
@Override
public void replaceAll(UnaryOperator<E> operator) {
throw new UnsupportedOperationException();
}
@Override
public void sort(Comparator<? super E> c) {
throw new UnsupportedOperationException();
}
public ListIterator<E> listIterator() {return listIterator(0);}
public ListIterator<E> listIterator(final int index) {
return new ListIterator<E>() {
private final ListIterator<? extends E> i
= list.listIterator(index);
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public boolean hasPrevious() {return i.hasPrevious();}
public E previous() {return i.previous();}
public int nextIndex() {return i.nextIndex();}
public int previousIndex() {return i.previousIndex();}
public void remove() {
throw new UnsupportedOperationException();
}
public void set(E e) {
throw new UnsupportedOperationException();
}
public void add(E e) {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
i.forEachRemaining(action);
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
}
private Object readResolve() {
return (list instanceof RandomAccess
? new UnmodifiableRandomAccessList<>(list)
: this);
}
}
/**
* @serial include
*/
static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
implements RandomAccess
{
UnmodifiableRandomAccessList(List<? extends E> list) {
super(list);
}
public List<E> subList(int fromIndex, int toIndex) {
return new UnmodifiableRandomAccessList<>(
list.subList(fromIndex, toIndex));
}
private static final long serialVersionUID = -2542308836966382001L;
/**
* Allows instances to be deserialized in pre-1.4 JREs (which do
* not have UnmodifiableRandomAccessList). UnmodifiableList has
* a readResolve method that inverts this transformation upon
* deserialization.
*/
private Object writeReplace() {
return new UnmodifiableList<>(list);
}
}
/**
* Returns an unmodifiable view of the specified map. This method
* allows modules to provide users with "read-only" access to internal
* maps. Query operations on the returned map "read through"
* to the specified map, and attempts to modify the returned
* map, whether direct or via its collection views, result in an
* <tt>UnsupportedOperationException</tt>.<p>
*
* The returned map will be serializable if the specified map
* is serializable.
*
* @param <K> the class of the map keys
* @param <V> the class of the map values
* @param m the map for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified map.
*/
public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
return new UnmodifiableMap<>(m);
}
/**
* @serial include
*/
private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
private static final long serialVersionUID = -1034234728574286014L;
private final Map<? extends K, ? extends V> m;
UnmodifiableMap(Map<? extends K, ? extends V> m) {
if (m==null)
throw new NullPointerException();
this.m = m;
}
public int size() {return m.size();}
public boolean isEmpty() {return m.isEmpty();}
public boolean containsKey(Object key) {return m.containsKey(key);}
public boolean containsValue(Object val) {return m.containsValue(val);}
public V get(Object key) {return m.get(key);}
public V put(K key, V value) {
throw new UnsupportedOperationException();
}
public V remove(Object key) {
throw new UnsupportedOperationException();
}
public void putAll(Map<? extends K, ? extends V> m) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
private transient Set<K> keySet;
private transient Set<Map.Entry<K,V>> entrySet;
private transient Collection<V> values;
public Set<K> keySet() {
if (keySet==null)
keySet = unmodifiableSet(m.keySet());
return keySet;
}
public Set<Map.Entry<K,V>> entrySet() {
if (entrySet==null)
entrySet = new UnmodifiableEntrySet<>(m.entrySet());
return entrySet;
}
public Collection<V> values() {
if (values==null)
values = unmodifiableCollection(m.values());
return values;
}
public boolean equals(Object o) {return o == this || m.equals(o);}
public int hashCode() {return m.hashCode();}
public String toString() {return m.toString();}
@Override
@SuppressWarnings("unchecked")
public V getOrDefault(Object k, V defaultValue) {
return ((Map<K, V>)m).getOrDefault(k, defaultValue);
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
m.forEach(action);
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
throw new UnsupportedOperationException();
}
@Override
public V putIfAbsent(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
throw new UnsupportedOperationException();
}
@Override
public V replace(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
static class UnmodifiableEntrySet<K,V>
extends UnmodifiableSet<Map.Entry<K,V>> {
private static final long serialVersionUID = 7854390611657943733L;
@SuppressWarnings({"unchecked", "rawtypes"})
UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
super((Set)s);
}
static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) {
return e -> action.accept(new UnmodifiableEntry<>(e));
}
public void forEach(Consumer<? super Entry<K, V>> action) {
Objects.requireNonNull(action);
c.forEach(entryConsumer(action));
}
static final class UnmodifiableEntrySetSpliterator<K, V>
implements Spliterator<Entry<K,V>> {
final Spliterator<Map.Entry<K, V>> s;
UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>> s) {
this.s = s;
}
@Override
public boolean tryAdvance(Consumer<? super Entry<K, V>> action) {
Objects.requireNonNull(action);
return s.tryAdvance(entryConsumer(action));
}
@Override
public void forEachRemaining(Consumer<? super Entry<K, V>> action) {
Objects.requireNonNull(action);
s.forEachRemaining(entryConsumer(action));
}
@Override
public Spliterator<Entry<K, V>> trySplit() {
Spliterator<Entry<K, V>> split = s.trySplit();
return split == null
? null
: new UnmodifiableEntrySetSpliterator<>(split);
}
@Override
public long estimateSize() {
return s.estimateSize();
}
@Override
public long getExactSizeIfKnown() {
return s.getExactSizeIfKnown();
}
@Override
public int characteristics() {
return s.characteristics();
}
@Override
public boolean hasCharacteristics(int characteristics) {
return s.hasCharacteristics(characteristics);
}
@Override
public Comparator<? super Entry<K, V>> getComparator() {
return s.getComparator();
}
}
@SuppressWarnings("unchecked")
public Spliterator<Entry<K,V>> spliterator() {
return new UnmodifiableEntrySetSpliterator<>(
(Spliterator<Map.Entry<K, V>>) c.spliterator());
}
@Override
public Stream<Entry<K,V>> stream() {
return StreamSupport.stream(spliterator(), false);
}
@Override
public Stream<Entry<K,V>> parallelStream() {
return StreamSupport.stream(spliterator(), true);
}
public Iterator<Map.Entry<K,V>> iterator() {
return new Iterator<Map.Entry<K,V>>() {
private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
public boolean hasNext() {
return i.hasNext();
}
public Map.Entry<K,V> next() {
return new UnmodifiableEntry<>(i.next());
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@SuppressWarnings("unchecked")
public Object[] toArray() {
Object[] a = c.toArray();
for (int i=0; i<a.length; i++)
a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]);
return a;
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
for (int i=0; i<arr.length; i++)
arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]);
if (arr.length > a.length)
return (T[])arr;
System.arraycopy(arr, 0, a, 0, arr.length);
if (a.length > arr.length)
a[arr.length] = null;
return a;
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
return c.contains(
new UnmodifiableEntry<>((Map.Entry<?,?>) o));
}
public boolean containsAll(Collection<?> coll) {
for (Object e : coll) {
if (!contains(e)) // Invokes safe contains() above
return false;
}
return true;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Set<?> s = (Set<?>) o;
if (s.size() != c.size())
return false;
return containsAll(s); // Invokes safe containsAll() above
}
private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
private Map.Entry<? extends K, ? extends V> e;
UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e)
{this.e = Objects.requireNonNull(e);}
public K getKey() {return e.getKey();}
public V getValue() {return e.getValue();}
public V setValue(V value) {
throw new UnsupportedOperationException();
}
public int hashCode() {return e.hashCode();}
public boolean equals(Object o) {
if (this == o)
return true;
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> t = (Map.Entry<?,?>)o;
return eq(e.getKey(), t.getKey()) &&
eq(e.getValue(), t.getValue());
}
public String toString() {return e.toString();}
}
}
}
public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
return new UnmodifiableSortedMap<>(m);
}
static class UnmodifiableSortedMap<K,V>
extends UnmodifiableMap<K,V>
implements SortedMap<K,V>, Serializable {
private static final long serialVersionUID = -8806743815996713206L;
private final SortedMap<K, ? extends V> sm;
UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; }
public Comparator<? super K> comparator() { return sm.comparator(); }
public SortedMap<K,V> subMap(K fromKey, K toKey)
{ return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); }
public SortedMap<K,V> headMap(K toKey)
{ return new UnmodifiableSortedMap<>(sm.headMap(toKey)); }
public SortedMap<K,V> tailMap(K fromKey)
{ return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); }
public K firstKey() { return sm.firstKey(); }
public K lastKey() { return sm.lastKey(); }
}
public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {
return new UnmodifiableNavigableMap<>(m);
}
static class UnmodifiableNavigableMap<K,V>
extends UnmodifiableSortedMap<K,V>
implements NavigableMap<K,V>, Serializable {
private static final long serialVersionUID = -4858195264774772197L;
/**
* A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve
* to preserve singleton property.
*
* @param <K> type of keys, if there were any, and of bounds
* @param <V> type of values, if there were any
*/
private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V>
implements Serializable {
private static final long serialVersionUID = -2239321462712562324L;
EmptyNavigableMap() { super(new TreeMap<K,V>()); }
@Override
public NavigableSet<K> navigableKeySet()
{ return emptyNavigableSet(); }
private Object readResolve() { return EMPTY_NAVIGABLE_MAP; }
}
private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP =
new EmptyNavigableMap<>();
private final NavigableMap<K, ? extends V> nm;
UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m)
{super(m); nm = m;}
public K lowerKey(K key) { return nm.lowerKey(key); }
public K floorKey(K key) { return nm.floorKey(key); }
public K ceilingKey(K key) { return nm.ceilingKey(key); }
public K higherKey(K key) { return nm.higherKey(key); }
@SuppressWarnings("unchecked")
public Entry<K, V> lowerEntry(K key) {
Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key);
return (null != lower)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(lower)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> floorEntry(K key) {
Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key);
return (null != floor)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(floor)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> ceilingEntry(K key) {
Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key);
return (null != ceiling)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(ceiling)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> higherEntry(K key) {
Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key);
return (null != higher)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(higher)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> firstEntry() {
Entry<K,V> first = (Entry<K, V>) nm.firstEntry();
return (null != first)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(first)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> lastEntry() {
Entry<K,V> last = (Entry<K, V>) nm.lastEntry();
return (null != last)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(last)
: null;
}
public Entry<K, V> pollFirstEntry()
{ throw new UnsupportedOperationException(); }
public Entry<K, V> pollLastEntry()
{ throw new UnsupportedOperationException(); }
public NavigableMap<K, V> descendingMap()
{ return unmodifiableNavigableMap(nm.descendingMap()); }
public NavigableSet<K> navigableKeySet()
{ return unmodifiableNavigableSet(nm.navigableKeySet()); }
public NavigableSet<K> descendingKeySet()
{ return unmodifiableNavigableSet(nm.descendingKeySet()); }
public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
return unmodifiableNavigableMap(
nm.subMap(fromKey, fromInclusive, toKey, toInclusive));
}
public NavigableMap<K, V> headMap(K toKey, boolean inclusive)
{ return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); }
public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive)
{ return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); }
}
/**
* 返回由指定集合支持的同步（线程安全）集合。
* 为了保证串行访问，至关重要的是所有对后备集合的访问都必须通过返回的集合来完成。
* 当通过{@link Iterator}，{@link Spliterator}或{@link Stream}遍历返回的集合时，
* 用户必须手动对其进行同步：
* Collection c = Collections.synchronizedCollection(myCollection);
* ...
* synchronized (c) {
* Iterator i = c.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*/
public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
return new SynchronizedCollection<>(c);
}
static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
return new SynchronizedCollection<>(c, mutex);
}
static class SynchronizedCollection<E> implements Collection<E>, Serializable {
private static final long serialVersionUID = 3053995032091335093L;
final Collection<E> c; // Backing Collection
final Object mutex; // Object on which to synchronize
SynchronizedCollection(Collection<E> c) {
this.c = Objects.requireNonNull(c);
mutex = this;
}
SynchronizedCollection(Collection<E> c, Object mutex) {
this.c = Objects.requireNonNull(c);
this.mutex = Objects.requireNonNull(mutex);
}
public int size() {
synchronized (mutex) {return c.size();}
}
public boolean isEmpty() {
synchronized (mutex) {return c.isEmpty();}
}
public boolean contains(Object o) {
synchronized (mutex) {return c.contains(o);}
}
public Object[] toArray() {
synchronized (mutex) {return c.toArray();}
}
public <T> T[] toArray(T[] a) {
synchronized (mutex) {return c.toArray(a);}
}
public Iterator<E> iterator() {
return c.iterator(); // Must be manually synched by user!
}
public boolean add(E e) {
synchronized (mutex) {return c.add(e);}
}
public boolean remove(Object o) {
synchronized (mutex) {return c.remove(o);}
}
public boolean containsAll(Collection<?> coll) {
synchronized (mutex) {return c.containsAll(coll);}
}
public boolean addAll(Collection<? extends E> coll) {
synchronized (mutex) {return c.addAll(coll);}
}
public boolean removeAll(Collection<?> coll) {
synchronized (mutex) {return c.removeAll(coll);}
}
public boolean retainAll(Collection<?> coll) {
synchronized (mutex) {return c.retainAll(coll);}
}
public void clear() {
synchronized (mutex) {c.clear();}
}
public String toString() {
synchronized (mutex) {return c.toString();}
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> consumer) {
synchronized (mutex) {c.forEach(consumer);}
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
synchronized (mutex) {return c.removeIf(filter);}
}
@Override
public Spliterator<E> spliterator() {
return c.spliterator(); // Must be manually synched by user!
}
@Override
public Stream<E> stream() {
return c.stream(); // Must be manually synched by user!
}
@Override
public Stream<E> parallelStream() {
return c.parallelStream(); // Must be manually synched by user!
}
private void writeObject(ObjectOutputStream s) throws IOException {
synchronized (mutex) {s.defaultWriteObject();}
}
}
/**
* Returns a synchronized (thread-safe) set backed by the specified
* set. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing set is accomplished
* through the returned set.<p>
* 返回由指定集合支持的同步（线程安全）集合。为了保证串行访问，至关重要的是，对后备集的所有访问都必须通过返回的集来完成。
*
* It is imperative that the user manually synchronize on the returned
* set when iterating over it:
* <pre>
* Set s = Collections.synchronizedSet(new HashSet());
* ...
* synchronized (s) {
* Iterator i = s.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* Failure to follow this advice may result in non-deterministic behavior.
*
* <p>The returned set will be serializable if the specified set is
* serializable.
*
* @param <T> the class of the objects in the set
* @param s the set to be "wrapped" in a synchronized set.
* @return a synchronized view of the specified set.
*/
public static <T> Set<T> synchronizedSet(Set<T> s) {
return new SynchronizedSet<>(s);
}
static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
return new SynchronizedSet<>(s, mutex);
}
/**
* @serial include
*/
static class SynchronizedSet<E>
extends SynchronizedCollection<E>
implements Set<E> {
private static final long serialVersionUID = 487447009682186044L;
SynchronizedSet(Set<E> s) {
super(s);
}
SynchronizedSet(Set<E> s, Object mutex) {
super(s, mutex);
}
public boolean equals(Object o) {
if (this == o)
return true;
synchronized (mutex) {return c.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return c.hashCode();}
}
}
public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
return new SynchronizedSortedSet<>(s);
}
static class SynchronizedSortedSet<E>
extends SynchronizedSet<E>
implements SortedSet<E>
{
private static final long serialVersionUID = 8695801310862127406L;
private final SortedSet<E> ss;
SynchronizedSortedSet(SortedSet<E> s) {
super(s);
ss = s;
}
SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
super(s, mutex);
ss = s;
}
public Comparator<? super E> comparator() {
synchronized (mutex) {return ss.comparator();}
}
public SortedSet<E> subSet(E fromElement, E toElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(
ss.subSet(fromElement, toElement), mutex);
}
}
public SortedSet<E> headSet(E toElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
}
}
public SortedSet<E> tailSet(E fromElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
}
}
public E first() {
synchronized (mutex) {return ss.first();}
}
public E last() {
synchronized (mutex) {return ss.last();}
}
}
public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) {
return new SynchronizedNavigableSet<>(s);
}
static class SynchronizedNavigableSet<E>
extends SynchronizedSortedSet<E>
implements NavigableSet<E>
{
private static final long serialVersionUID = -5505529816273629798L;
private final NavigableSet<E> ns;
SynchronizedNavigableSet(NavigableSet<E> s) {
super(s);
ns = s;
}
SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) {
super(s, mutex);
ns = s;
}
public E lower(E e) { synchronized (mutex) {return ns.lower(e);} }
public E floor(E e) { synchronized (mutex) {return ns.floor(e);} }
public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} }
public E higher(E e) { synchronized (mutex) {return ns.higher(e);} }
public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} }
public E pollLast() { synchronized (mutex) {return ns.pollLast();} }
public NavigableSet<E> descendingSet() {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex);
}
}
public Iterator<E> descendingIterator()
{ synchronized (mutex) { return descendingSet().iterator(); } }
public NavigableSet<E> subSet(E fromElement, E toElement) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex);
}
}
public NavigableSet<E> headSet(E toElement) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex);
}
}
public NavigableSet<E> tailSet(E fromElement) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, true), mutex);
}
}
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex);
}
}
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex);
}
}
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive), mutex);
}
}
}
public static <T> List<T> synchronizedList(List<T> list) {
return (list instanceof RandomAccess ?
new SynchronizedRandomAccessList<>(list) :
new SynchronizedList<>(list));
}
static <T> List<T> synchronizedList(List<T> list, Object mutex) {
return (list instanceof RandomAccess ?
new SynchronizedRandomAccessList<>(list, mutex) :
new SynchronizedList<>(list, mutex));
}
static class SynchronizedList<E>
extends SynchronizedCollection<E>
implements List<E> {
private static final long serialVersionUID = -7754090372962971524L;
final List<E> list;
SynchronizedList(List<E> list) {
super(list);
this.list = list;
}
SynchronizedList(List<E> list, Object mutex) {
super(list, mutex);
this.list = list;
}
public boolean equals(Object o) {
if (this == o)
return true;
synchronized (mutex) {return list.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return list.hashCode();}
}
public E get(int index) {
synchronized (mutex) {return list.get(index);}
}
public E set(int index, E element) {
synchronized (mutex) {return list.set(index, element);}
}
public void add(int index, E element) {
synchronized (mutex) {list.add(index, element);}
}
public E remove(int index) {
synchronized (mutex) {return list.remove(index);}
}
public int indexOf(Object o) {
synchronized (mutex) {return list.indexOf(o);}
}
public int lastIndexOf(Object o) {
synchronized (mutex) {return list.lastIndexOf(o);}
}
public boolean addAll(int index, Collection<? extends E> c) {
synchronized (mutex) {return list.addAll(index, c);}
}
public ListIterator<E> listIterator() {
return list.listIterator(); // Must be manually synched by user
}
public ListIterator<E> listIterator(int index) {
return list.listIterator(index); // Must be manually synched by user
}
public List<E> subList(int fromIndex, int toIndex) {
synchronized (mutex) {
return new SynchronizedList<>(list.subList(fromIndex, toIndex),
mutex);
}
}
@Override
public void replaceAll(UnaryOperator<E> operator) {
synchronized (mutex) {list.replaceAll(operator);}
}
@Override
public void sort(Comparator<? super E> c) {
synchronized (mutex) {list.sort(c);}
}
private Object readResolve() {
return (list instanceof RandomAccess
? new SynchronizedRandomAccessList<>(list)
: this);
}
}
static class SynchronizedRandomAccessList<E>
extends SynchronizedList<E>
implements RandomAccess {
SynchronizedRandomAccessList(List<E> list) {
super(list);
}
SynchronizedRandomAccessList(List<E> list, Object mutex) {
super(list, mutex);
}
public List<E> subList(int fromIndex, int toIndex) {
synchronized (mutex) {
return new SynchronizedRandomAccessList<>(
list.subList(fromIndex, toIndex), mutex);
}
}
private static final long serialVersionUID = 1530674583602358482L;
/**
* Allows instances to be deserialized in pre-1.4 JREs (which do
* not have SynchronizedRandomAccessList). SynchronizedList has
* a readResolve method that inverts this transformation upon
* deserialization.
*/
private Object writeReplace() {
return new SynchronizedList<>(list);
}
}
public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
return new SynchronizedMap<>(m);
}
/**
* @serial include
*/
private static class SynchronizedMap<K,V>
implements Map<K,V>, Serializable {
private static final long serialVersionUID = 1978198479659022715L;
private final Map<K,V> m; // Backing Map
final Object mutex; // Object on which to synchronize
SynchronizedMap(Map<K,V> m) {
this.m = Objects.requireNonNull(m);
mutex = this;
}
SynchronizedMap(Map<K,V> m, Object mutex) {
this.m = m;
this.mutex = mutex;
}
public int size() {
synchronized (mutex) {return m.size();}
}
public boolean isEmpty() {
synchronized (mutex) {return m.isEmpty();}
}
public boolean containsKey(Object key) {
synchronized (mutex) {return m.containsKey(key);}
}
public boolean containsValue(Object value) {
synchronized (mutex) {return m.containsValue(value);}
}
public V get(Object key) {
synchronized (mutex) {return m.get(key);}
}
public V put(K key, V value) {
synchronized (mutex) {return m.put(key, value);}
}
public V remove(Object key) {
synchronized (mutex) {return m.remove(key);}
}
public void putAll(Map<? extends K, ? extends V> map) {
synchronized (mutex) {m.putAll(map);}
}
public void clear() {
synchronized (mutex) {m.clear();}
}
private transient Set<K> keySet;
private transient Set<Map.Entry<K,V>> entrySet;
private transient Collection<V> values;
public Set<K> keySet() {
synchronized (mutex) {
if (keySet==null)
keySet = new SynchronizedSet<>(m.keySet(), mutex);
return keySet;
}
}
public Set<Map.Entry<K,V>> entrySet() {
synchronized (mutex) {
if (entrySet==null)
entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
return entrySet;
}
}
public Collection<V> values() {
synchronized (mutex) {
if (values==null)
values = new SynchronizedCollection<>(m.values(), mutex);
return values;
}
}
public boolean equals(Object o) {
if (this == o)
return true;
synchronized (mutex) {return m.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return m.hashCode();}
}
public String toString() {
synchronized (mutex) {return m.toString();}
}
// Override default methods in Map
@Override
public V getOrDefault(Object k, V defaultValue) {
synchronized (mutex) {return m.getOrDefault(k, defaultValue);}
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
synchronized (mutex) {m.forEach(action);}
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
synchronized (mutex) {m.replaceAll(function);}
}
@Override
public V putIfAbsent(K key, V value) {
synchronized (mutex) {return m.putIfAbsent(key, value);}
}
@Override
public boolean remove(Object key, Object value) {
synchronized (mutex) {return m.remove(key, value);}
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
synchronized (mutex) {return m.replace(key, oldValue, newValue);}
}
@Override
public V replace(K key, V value) {
synchronized (mutex) {return m.replace(key, value);}
}
@Override
public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);}
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);}
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
synchronized (mutex) {return m.compute(key, remappingFunction);}
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
synchronized (mutex) {return m.merge(key, value, remappingFunction);}
}
private void writeObject(ObjectOutputStream s) throws IOException {
synchronized (mutex) {s.defaultWriteObject();}
}
}
public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
return new SynchronizedSortedMap<>(m);
}
/**
* @serial include
*/
static class SynchronizedSortedMap<K,V>
extends SynchronizedMap<K,V>
implements SortedMap<K,V>
{
private static final long serialVersionUID = -8798146769416483793L;
private final SortedMap<K,V> sm;
SynchronizedSortedMap(SortedMap<K,V> m) {
super(m);
sm = m;
}
SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
super(m, mutex);
sm = m;
}
public Comparator<? super K> comparator() {
synchronized (mutex) {return sm.comparator();}
}
public SortedMap<K,V> subMap(K fromKey, K toKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(
sm.subMap(fromKey, toKey), mutex);
}
}
public SortedMap<K,V> headMap(K toKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
}
}
public SortedMap<K,V> tailMap(K fromKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
}
}
public K firstKey() {
synchronized (mutex) {return sm.firstKey();}
}
public K lastKey() {
synchronized (mutex) {return sm.lastKey();}
}
}
public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) {
return new SynchronizedNavigableMap<>(m);
}
/**
* A synchronized NavigableMap.
*
* @serial include
*/
static class SynchronizedNavigableMap<K,V>
extends SynchronizedSortedMap<K,V>
implements NavigableMap<K,V>
{
private static final long serialVersionUID = 699392247599746807L;
private final NavigableMap<K,V> nm;
SynchronizedNavigableMap(NavigableMap<K,V> m) {
super(m);
nm = m;
}
SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) {
super(m, mutex);
nm = m;
}
public Entry<K, V> lowerEntry(K key)
{ synchronized (mutex) { return nm.lowerEntry(key); } }
public K lowerKey(K key)
{ synchronized (mutex) { return nm.lowerKey(key); } }
public Entry<K, V> floorEntry(K key)
{ synchronized (mutex) { return nm.floorEntry(key); } }
public K floorKey(K key)
{ synchronized (mutex) { return nm.floorKey(key); } }
public Entry<K, V> ceilingEntry(K key)
{ synchronized (mutex) { return nm.ceilingEntry(key); } }
public K ceilingKey(K key)
{ synchronized (mutex) { return nm.ceilingKey(key); } }
public Entry<K, V> higherEntry(K key)
{ synchronized (mutex) { return nm.higherEntry(key); } }
public K higherKey(K key)
{ synchronized (mutex) { return nm.higherKey(key); } }
public Entry<K, V> firstEntry()
{ synchronized (mutex) { return nm.firstEntry(); } }
public Entry<K, V> lastEntry()
{ synchronized (mutex) { return nm.lastEntry(); } }
public Entry<K, V> pollFirstEntry()
{ synchronized (mutex) { return nm.pollFirstEntry(); } }
public Entry<K, V> pollLastEntry()
{ synchronized (mutex) { return nm.pollLastEntry(); } }
public NavigableMap<K, V> descendingMap() {
synchronized (mutex) {
return
new SynchronizedNavigableMap<>(nm.descendingMap(), mutex);
}
}
public NavigableSet<K> keySet() {
return navigableKeySet();
}
public NavigableSet<K> navigableKeySet() {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(nm.navigableKeySet(), mutex);
}
}
public NavigableSet<K> descendingKeySet() {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(nm.descendingKeySet(), mutex);
}
}
public SortedMap<K,V> subMap(K fromKey, K toKey) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.subMap(fromKey, true, toKey, false), mutex);
}
}
public SortedMap<K,V> headMap(K toKey) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex);
}
}
public SortedMap<K,V> tailMap(K fromKey) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex);
}
}
public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex);
}
}
public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.headMap(toKey, inclusive), mutex);
}
}
public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.tailMap(fromKey, inclusive), mutex);
}
}
}
// Dynamically typesafe collection wrappers
/**
* 返回指定集合的动态类型安全视图。
* 任何尝试插入错误类型的元素的尝试都会立即导致{@link ClassCastException}。
* 假设在生成动态类型安全视图之前，集合中不包含任何类型错误的元素，
* 并且所有后续对该集合的访问都是通过该视图进行的，
* 那么可以确保该集合中不能包含类型错误的元素。
* 该语言中的泛型机制提供了编译时（静态）类型检查，
* 但是有可能通过未经检查的强制转换来破坏该机制。
* 通常这不是问题，因为编译器会针对所有此类未经检查的操作发出警告。
* 但是，有时仅靠静态类型检查是不够的。
* 例如，假设将一个集合传递给第三方库，并且必须通过插入错误类型的元素来使库代码不破坏该集合。
* 动态类型安全视图的另一种用法是调试。
* 假设程序失败，并显示{@code ClassCastException}，表示将错误键入的元素放入参数化集合中。
* 不幸的是，异常可能会在插入错误元素后的任何时间发生，
* 因此，对于问题的真正根源，它通常提供的信息很少或没有。
* 如果问题是可重现的，则可以通过临时修改程序以使用动态类型安全视图包装集合来快速确定其来源。
*
* 再次运行该程序将导致它在将错误键入的元素插入到集合中时失败，
* 从而清楚地确定问题的根源。
* 解决问题后，可以将修改后的声明还原为原始声明。
* 返回的集合不会将hashCode和equals操作传递到后备集合，
* 而是依赖于{@code Object}的{@code equals}和{@code hashCode}方法。
* 在后备集合是集合或列表的情况下，必须保留这些操作的合同。
* 如果指定的集合是可序列化的，则返回的集合将是可序列化的。
* 由于{@code null}被认为是任何引用类型的值，因此只要后备集合可以，返回的集合就允许插入null元素。
*
*/
public static <E> Collection<E> checkedCollection(Collection<E> c,
Class<E> type) {
return new CheckedCollection<>(c, type);
}
@SuppressWarnings("unchecked")
static <T> T[] zeroLengthArray(Class<T> type) {
return (T[]) Array.newInstance(type, 0);
}
/**
* @serial include
*/
static class CheckedCollection<E> implements Collection<E>, Serializable {
private static final long serialVersionUID = 1578914078182001775L;
final Collection<E> c;
final Class<E> type;
@SuppressWarnings("unchecked")
E typeCheck(Object o) {
if (o != null && !type.isInstance(o))
throw new ClassCastException(badElementMsg(o));
return (E) o;
}
private String badElementMsg(Object o) {
return "Attempt to insert " + o.getClass() +
" element into collection with element type " + type;
}
CheckedCollection(Collection<E> c, Class<E> type) {
this.c = Objects.requireNonNull(c, "c");
this.type = Objects.requireNonNull(type, "type");
}
public int size() { return c.size(); }
public boolean isEmpty() { return c.isEmpty(); }
public boolean contains(Object o) { return c.contains(o); }
public Object[] toArray() { return c.toArray(); }
public <T> T[] toArray(T[] a) { return c.toArray(a); }
public String toString() { return c.toString(); }
public boolean remove(Object o) { return c.remove(o); }
public void clear() { c.clear(); }
public boolean containsAll(Collection<?> coll) {
return c.containsAll(coll);
}
public boolean removeAll(Collection<?> coll) {
return c.removeAll(coll);
}
public boolean retainAll(Collection<?> coll) {
return c.retainAll(coll);
}
public Iterator<E> iterator() {
// JDK-6363904 - unwrapped iterator could be typecast to
// ListIterator with unsafe set()
final Iterator<E> it = c.iterator();
return new Iterator<E>() {
public boolean hasNext() { return it.hasNext(); }
public E next() { return it.next(); }
public void remove() { it.remove(); }};
}
public boolean add(E e) { return c.add(typeCheck(e)); }
private E[] zeroLengthElementArray; // Lazily initialized
private E[] zeroLengthElementArray() {
return zeroLengthElementArray != null ? zeroLengthElementArray :
(zeroLengthElementArray = zeroLengthArray(type));
}
@SuppressWarnings("unchecked")
Collection<E> checkedCopyOf(Collection<? extends E> coll) {
Object[] a;
try {
E[] z = zeroLengthElementArray();
a = coll.toArray(z);
// Defend against coll violating the toArray contract
if (a.getClass() != z.getClass())
a = Arrays.copyOf(a, a.length, z.getClass());
} catch (ArrayStoreException ignore) {
// To get better and consistent diagnostics,
// we call typeCheck explicitly on each element.
// We call clone() to defend against coll retaining a
// reference to the returned array and storing a bad
// element into it after it has been type checked.
a = coll.toArray().clone();
for (Object o : a)
typeCheck(o);
}
// A slight abuse of the type system, but safe here.
return (Collection<E>) Arrays.asList(a);
}
public boolean addAll(Collection<? extends E> coll) {
return c.addAll(checkedCopyOf(coll));
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {c.forEach(action);}
@Override
public boolean removeIf(Predicate<? super E> filter) {
return c.removeIf(filter);
}
@Override
public Spliterator<E> spliterator() {return c.spliterator();}
@Override
public Stream<E> stream() {return c.stream();}
@Override
public Stream<E> parallelStream() {return c.parallelStream();}
}
/**
* 返回指定队列的动态类型安全视图。
* 任何尝试插入错误类型的元素的尝试都会立即导致{@link ClassCastException}。
* 假设在生成动态类型安全视图之前，队列中不包含任何类型错误的元素，并且所有后续对该队列的访问都是通过该视图进行的，
* 那么可以保证该队列中不能包含类型错误的元素。
* 有关使用动态类型安全视图的讨论，可以在{@link
* 如果指定的队列可序列化，则返回的队列将可序列化。
* 由于{@code null}被认为是任何引用类型的值，因此只要后备队列允许，返回的队列就允许插入{@code null}元素。
*/
public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) {
return new CheckedQueue<>(queue, type);
}
/**
* @serial include
*/
static class CheckedQueue<E>
extends CheckedCollection<E>
implements Queue<E>, Serializable
{
private static final long serialVersionUID = 1433151992604707767L;
final Queue<E> queue;
CheckedQueue(Queue<E> queue, Class<E> elementType) {
super(queue, elementType);
this.queue = queue;
}
public E element() {return queue.element();}
public boolean equals(Object o) {return o == this || c.equals(o);}
public int hashCode() {return c.hashCode();}
public E peek() {return queue.peek();}
public E poll() {return queue.poll();}
public E remove() {return queue.remove();}
public boolean offer(E e) {return queue.offer(typeCheck(e));}
}
/**
* Returns a dynamically typesafe view of the specified set.
* Any attempt to insert an element of the wrong type will result in
* an immediate {@link ClassCastException}. Assuming a set contains
* no incorrectly typed elements prior to the time a dynamically typesafe
* view is generated, and that all subsequent access to the set
* takes place through the view, it is <i>guaranteed</i> that the
* set cannot contain an incorrectly typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link
* checkedCollection} method.
*
* <p>The returned set will be serializable if the specified set is
* serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned set permits insertion of null elements whenever
* the backing set does.
*
* @param <E> the class of the objects in the set
* @param s the set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified set
* @since 1.5
*/
public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
return new CheckedSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedSet<E> extends CheckedCollection<E>
implements Set<E>, Serializable
{
private static final long serialVersionUID = 4694047833775013803L;
CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
public boolean equals(Object o) { return o == this || c.equals(o); }
public int hashCode() { return c.hashCode(); }
}
/**
* Returns a dynamically typesafe view of the specified sorted set.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a sorted set
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the sorted set takes place through the view, it is
* <i>guaranteed</i> that the sorted set cannot contain an incorrectly
* typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link
* checkedCollection} method.
*
* <p>The returned sorted set will be serializable if the specified sorted
* set is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned sorted set permits insertion of null elements
* whenever the backing sorted set does.
*
* @param <E> the class of the objects in the set
* @param s the sorted set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified sorted set
* @since 1.5
*/
public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
Class<E> type) {
return new CheckedSortedSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedSortedSet<E> extends CheckedSet<E>
implements SortedSet<E>, Serializable
{
private static final long serialVersionUID = 1599911165492914959L;
private final SortedSet<E> ss;
CheckedSortedSet(SortedSet<E> s, Class<E> type) {
super(s, type);
ss = s;
}
public Comparator<? super E> comparator() { return ss.comparator(); }
public E first() { return ss.first(); }
public E last() { return ss.last(); }
public SortedSet<E> subSet(E fromElement, E toElement) {
return checkedSortedSet(ss.subSet(fromElement,toElement), type);
}
public SortedSet<E> headSet(E toElement) {
return checkedSortedSet(ss.headSet(toElement), type);
}
public SortedSet<E> tailSet(E fromElement) {
return checkedSortedSet(ss.tailSet(fromElement), type);
}
}
/**
* Returns a dynamically typesafe view of the specified navigable set.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a navigable set
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the navigable set takes place through the view, it is
* <em>guaranteed</em> that the navigable set cannot contain an incorrectly
* typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link
* checkedCollection} method.
*
* <p>The returned navigable set will be serializable if the specified
* navigable set is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned navigable set permits insertion of null elements
* whenever the backing sorted set does.
*
* @param <E> the class of the objects in the set
* @param s the navigable set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified navigable set
* @since 1.8
*/
public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s,
Class<E> type) {
return new CheckedNavigableSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedNavigableSet<E> extends CheckedSortedSet<E>
implements NavigableSet<E>, Serializable
{
private static final long serialVersionUID = -5429120189805438922L;
private final NavigableSet<E> ns;
CheckedNavigableSet(NavigableSet<E> s, Class<E> type) {
super(s, type);
ns = s;
}
public E lower(E e) { return ns.lower(e); }
public E floor(E e) { return ns.floor(e); }
public E ceiling(E e) { return ns.ceiling(e); }
public E higher(E e) { return ns.higher(e); }
public E pollFirst() { return ns.pollFirst(); }
public E pollLast() {return ns.pollLast(); }
public NavigableSet<E> descendingSet()
{ return checkedNavigableSet(ns.descendingSet(), type); }
public Iterator<E> descendingIterator()
{return checkedNavigableSet(ns.descendingSet(), type).iterator(); }
public NavigableSet<E> subSet(E fromElement, E toElement) {
return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type);
}
public NavigableSet<E> headSet(E toElement) {
return checkedNavigableSet(ns.headSet(toElement, false), type);
}
public NavigableSet<E> tailSet(E fromElement) {
return checkedNavigableSet(ns.tailSet(fromElement, true), type);
}
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type);
}
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
return checkedNavigableSet(ns.headSet(toElement, inclusive), type);
}
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type);
}
}
/**
* Returns a dynamically typesafe view of the specified list.
* Any attempt to insert an element of the wrong type will result in
* an immediate {@link ClassCastException}. Assuming a list contains
* no incorrectly typed elements prior to the time a dynamically typesafe
* view is generated, and that all subsequent access to the list
* takes place through the view, it is <i>guaranteed</i> that the
* list cannot contain an incorrectly typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link
* checkedCollection} method.
*
* <p>The returned list will be serializable if the specified list
* is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned list permits insertion of null elements whenever
* the backing list does.
*
* @param <E> the class of the objects in the list
* @param list the list for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code list} is permitted to hold
* @return a dynamically typesafe view of the specified list
* @since 1.5
*/
public static <E> List<E> checkedList(List<E> list, Class<E> type) {
return (list instanceof RandomAccess ?
new CheckedRandomAccessList<>(list, type) :
new CheckedList<>(list, type));
}
/**
* @serial include
*/
static class CheckedList<E>
extends CheckedCollection<E>
implements List<E>
{
private static final long serialVersionUID = 65247728283967356L;
final List<E> list;
CheckedList(List<E> list, Class<E> type) {
super(list, type);
this.list = list;
}
public boolean equals(Object o) { return o == this || list.equals(o); }
public int hashCode() { return list.hashCode(); }
public E get(int index) { return list.get(index); }
public E remove(int index) { return list.remove(index); }
public int indexOf(Object o) { return list.indexOf(o); }
public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
public E set(int index, E element) {
return list.set(index, typeCheck(element));
}
public void add(int index, E element) {
list.add(index, typeCheck(element));
}
public boolean addAll(int index, Collection<? extends E> c) {
return list.addAll(index, checkedCopyOf(c));
}
public ListIterator<E> listIterator() { return listIterator(0); }
public ListIterator<E> listIterator(final int index) {
final ListIterator<E> i = list.listIterator(index);
return new ListIterator<E>() {
public boolean hasNext() { return i.hasNext(); }
public E next() { return i.next(); }
public boolean hasPrevious() { return i.hasPrevious(); }
public E previous() { return i.previous(); }
public int nextIndex() { return i.nextIndex(); }
public int previousIndex() { return i.previousIndex(); }
public void remove() { i.remove(); }
public void set(E e) {
i.set(typeCheck(e));
}
public void add(E e) {
i.add(typeCheck(e));
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
i.forEachRemaining(action);
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
return new CheckedList<>(list.subList(fromIndex, toIndex), type);
}
/**
* {@inheritDoc}
*
* @throws ClassCastException if the class of an element returned by the
* operator prevents it from being added to this collection. The
* exception may be thrown after some elements of the list have
* already been replaced.
*/
@Override
public void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
list.replaceAll(e -> typeCheck(operator.apply(e)));
}
@Override
public void sort(Comparator<? super E> c) {
list.sort(c);
}
}
/**
* @serial include
*/
static class CheckedRandomAccessList<E> extends CheckedList<E>
implements RandomAccess
{
private static final long serialVersionUID = 1638200125423088369L;
CheckedRandomAccessList(List<E> list, Class<E> type) {
super(list, type);
}
public List<E> subList(int fromIndex, int toIndex) {
return new CheckedRandomAccessList<>(
list.subList(fromIndex, toIndex), type);
}
}
public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
Class<K> keyType,
Class<V> valueType) {
return new CheckedMap<>(m, keyType, valueType);
}
/**
* @serial include
*/
private static class CheckedMap<K,V>
implements Map<K,V>, Serializable
{
private static final long serialVersionUID = 5742860141034234728L;
private final Map<K, V> m;
final Class<K> keyType;
final Class<V> valueType;
private void typeCheck(Object key, Object value) {
if (key != null && !keyType.isInstance(key))
throw new ClassCastException(badKeyMsg(key));
if (value != null && !valueType.isInstance(value))
throw new ClassCastException(badValueMsg(value));
}
private BiFunction<? super K, ? super V, ? extends V> typeCheck(
BiFunction<? super K, ? super V, ? extends V> func) {
Objects.requireNonNull(func);
return (k, v) -> {
V newValue = func.apply(k, v);
typeCheck(k, newValue);
return newValue;
};
}
private String badKeyMsg(Object key) {
return "Attempt to insert " + key.getClass() +
" key into map with key type " + keyType;
}
private String badValueMsg(Object value) {
return "Attempt to insert " + value.getClass() +
" value into map with value type " + valueType;
}
CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
this.m = Objects.requireNonNull(m);
this.keyType = Objects.requireNonNull(keyType);
this.valueType = Objects.requireNonNull(valueType);
}
public int size() { return m.size(); }
public boolean isEmpty() { return m.isEmpty(); }
public boolean containsKey(Object key) { return m.containsKey(key); }
public boolean containsValue(Object v) { return m.containsValue(v); }
public V get(Object key) { return m.get(key); }
public V remove(Object key) { return m.remove(key); }
public void clear() { m.clear(); }
public Set<K> keySet() { return m.keySet(); }
public Collection<V> values() { return m.values(); }
public boolean equals(Object o) { return o == this || m.equals(o); }
public int hashCode() { return m.hashCode(); }
public String toString() { return m.toString(); }
public V put(K key, V value) {
typeCheck(key, value);
return m.put(key, value);
}
@SuppressWarnings("unchecked")
public void putAll(Map<? extends K, ? extends V> t) {
// Satisfy the following goals:
// - good diagnostics in case of type mismatch
// - all-or-nothing semantics
// - protection from malicious t
// - correct behavior if t is a concurrent map
Object[] entries = t.entrySet().toArray();
List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length);
for (Object o : entries) {
Map.Entry<?,?> e = (Map.Entry<?,?>) o;
Object k = e.getKey();
Object v = e.getValue();
typeCheck(k, v);
checked.add(
new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v));
}
for (Map.Entry<K,V> e : checked)
m.put(e.getKey(), e.getValue());
}
private transient Set<Map.Entry<K,V>> entrySet;
public Set<Map.Entry<K,V>> entrySet() {
if (entrySet==null)
entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
return entrySet;
}
// Override default methods in Map
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
m.forEach(action);
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
m.replaceAll(typeCheck(function));
}
@Override
public V putIfAbsent(K key, V value) {
typeCheck(key, value);
return m.putIfAbsent(key, value);
}
@Override
public boolean remove(Object key, Object value) {
return m.remove(key, value);
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
typeCheck(key, newValue);
return m.replace(key, oldValue, newValue);
}
@Override
public V replace(K key, V value) {
typeCheck(key, value);
return m.replace(key, value);
}
@Override
public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
Objects.requireNonNull(mappingFunction);
return m.computeIfAbsent(key, k -> {
V value = mappingFunction.apply(k);
typeCheck(k, value);
return value;
});
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
return m.computeIfPresent(key, typeCheck(remappingFunction));
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
return m.compute(key, typeCheck(remappingFunction));
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction);
return m.merge(key, value, (v1, v2) -> {
V newValue = remappingFunction.apply(v1, v2);
typeCheck(null, newValue);
return newValue;
});
}
/**
* We need this class in addition to CheckedSet as Map.Entry permits
* modification of the backing Map via the setValue operation. This
* class is subtle: there are many possible attacks that must be
* thwarted.
*
* @serial exclude
*/
static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
private final Set<Map.Entry<K,V>> s;
private final Class<V> valueType;
CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
this.s = s;
this.valueType = valueType;
}
public int size() { return s.size(); }
public boolean isEmpty() { return s.isEmpty(); }
public String toString() { return s.toString(); }
public int hashCode() { return s.hashCode(); }
public void clear() { s.clear(); }
public boolean add(Map.Entry<K, V> e) {
throw new UnsupportedOperationException();
}
public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
throw new UnsupportedOperationException();
}
public Iterator<Map.Entry<K,V>> iterator() {
final Iterator<Map.Entry<K, V>> i = s.iterator();
final Class<V> valueType = this.valueType;
return new Iterator<Map.Entry<K,V>>() {
public boolean hasNext() { return i.hasNext(); }
public void remove() { i.remove(); }
public Map.Entry<K,V> next() {
return checkedEntry(i.next(), valueType);
}
};
}
@SuppressWarnings("unchecked")
public Object[] toArray() {
Object[] source = s.toArray();
Object[] dest = (CheckedEntry.class.isInstance(
source.getClass().getComponentType()) ? source :
new Object[source.length]);
for (int i = 0; i < source.length; i++)
dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
valueType);
return dest;
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
for (int i=0; i<arr.length; i++)
arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
valueType);
if (arr.length > a.length)
return arr;
System.arraycopy(arr, 0, a, 0, arr.length);
if (a.length > arr.length)
a[arr.length] = null;
return a;
}
/**
* This method is overridden to protect the backing set against
* an object with a nefarious equals function that senses
* that the equality-candidate is Map.Entry and calls its
* setValue method.
*/
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> e = (Map.Entry<?,?>) o;
return s.contains(
(e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
}
/**
* The bulk collection methods are overridden to protect
* against an unscrupulous collection whose contains(Object o)
* method senses when o is a Map.Entry, and calls o.setValue.
*/
public boolean containsAll(Collection<?> c) {
for (Object o : c)
if (!contains(o)) // Invokes safe contains() above
return false;
return true;
}
public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
return s.remove(new AbstractMap.SimpleImmutableEntry
<>((Map.Entry<?,?>)o));
}
public boolean removeAll(Collection<?> c) {
return batchRemove(c, false);
}
public boolean retainAll(Collection<?> c) {
return batchRemove(c, true);
}
private boolean batchRemove(Collection<?> c, boolean complement) {
Objects.requireNonNull(c);
boolean modified = false;
Iterator<Map.Entry<K,V>> it = iterator();
while (it.hasNext()) {
if (c.contains(it.next()) != complement) {
it.remove();
modified = true;
}
}
return modified;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Set<?> that = (Set<?>) o;
return that.size() == s.size()
&& containsAll(that); // Invokes safe containsAll() above
}
static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
Class<T> valueType) {
return new CheckedEntry<>(e, valueType);
}
/**
* This "wrapper class" serves two purposes: it prevents
* the client from modifying the backing Map, by short-circuiting
* the setValue method, and it protects the backing Map against
* an ill-behaved Map.Entry that attempts to modify another
* Map.Entry when asked to perform an equality check.
*/
private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
private final Map.Entry<K, V> e;
private final Class<T> valueType;
CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
this.e = Objects.requireNonNull(e);
this.valueType = Objects.requireNonNull(valueType);
}
public K getKey() { return e.getKey(); }
public V getValue() { return e.getValue(); }
public int hashCode() { return e.hashCode(); }
public String toString() { return e.toString(); }
public V setValue(V value) {
if (value != null && !valueType.isInstance(value))
throw new ClassCastException(badValueMsg(value));
return e.setValue(value);
}
private String badValueMsg(Object value) {
return "Attempt to insert " + value.getClass() +
" value into map with value type " + valueType;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Map.Entry))
return false;
return e.equals(new AbstractMap.SimpleImmutableEntry
<>((Map.Entry<?,?>)o));
}
}
}
}
public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
Class<K> keyType,
Class<V> valueType) {
return new CheckedSortedMap<>(m, keyType, valueType);
}
/**
* @serial include
*/
static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
implements SortedMap<K,V>, Serializable
{
private static final long serialVersionUID = 1599671320688067438L;
private final SortedMap<K, V> sm;
CheckedSortedMap(SortedMap<K, V> m,
Class<K> keyType, Class<V> valueType) {
super(m, keyType, valueType);
sm = m;
}
public Comparator<? super K> comparator() { return sm.comparator(); }
public K firstKey() { return sm.firstKey(); }
public K lastKey() { return sm.lastKey(); }
public SortedMap<K,V> subMap(K fromKey, K toKey) {
return checkedSortedMap(sm.subMap(fromKey, toKey),
keyType, valueType);
}
public SortedMap<K,V> headMap(K toKey) {
return checkedSortedMap(sm.headMap(toKey), keyType, valueType);
}
public SortedMap<K,V> tailMap(K fromKey) {
return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType);
}
}
public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m,
Class<K> keyType,
Class<V> valueType) {
return new CheckedNavigableMap<>(m, keyType, valueType);
}
/**
* @serial include
*/
static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V>
implements NavigableMap<K,V>, Serializable
{
private static final long serialVersionUID = -4852462692372534096L;
private final NavigableMap<K, V> nm;
CheckedNavigableMap(NavigableMap<K, V> m,
Class<K> keyType, Class<V> valueType) {
super(m, keyType, valueType);
nm = m;
}
public Comparator<? super K> comparator() { return nm.comparator(); }
public K firstKey() { return nm.firstKey(); }
public K lastKey() { return nm.lastKey(); }
public Entry<K, V> lowerEntry(K key) {
Entry<K,V> lower = nm.lowerEntry(key);
return (null != lower)
? new CheckedMap.CheckedEntrySet.CheckedEntry<>(lower, valueType)
: null;
}
public K lowerKey(K key) { return nm.lowerKey(key); }
public Entry<K, V> floorEntry(K key) {
Entry<K,V> floor = nm.floorEntry(key);
return (null != floor)
? new CheckedMap.CheckedEntrySet.CheckedEntry<>(floor, valueType)
: null;
}
public K floorKey(K key) { return nm.floorKey(key); }
public Entry<K, V> ceilingEntry(K key) {
Entry<K,V> ceiling = nm.ceilingEntry(key);
return (null != ceiling)
? new CheckedMap.CheckedEntrySet.CheckedEntry<>(ceiling, valueType)
: null;
}
public K ceilingKey(K key) { return nm.ceilingKey(key); }
public Entry<K, V> higherEntry(K key) {
Entry<K,V> higher = nm.higherEntry(key);
return (null != higher)
? new CheckedMap.CheckedEntrySet.CheckedEntry<>(higher, valueType)
: null;
}
public K higherKey(K key) { return nm.higherKey(key); }
public Entry<K, V> firstEntry() {
Entry<K,V> first = nm.firstEntry();
return (null != first)
? new CheckedMap.CheckedEntrySet.CheckedEntry<>(first, valueType)
: null;
}
public Entry<K, V> lastEntry() {
Entry<K,V> last = nm.lastEntry();
return (null != last)
? new CheckedMap.CheckedEntrySet.CheckedEntry<>(last, valueType)
: null;
}
public Entry<K, V> pollFirstEntry() {
Entry<K,V> entry = nm.pollFirstEntry();
return (null == entry)
? null
: new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType);
}
public Entry<K, V> pollLastEntry() {
Entry<K,V> entry = nm.pollLastEntry();
return (null == entry)
? null
: new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType);
}
public NavigableMap<K, V> descendingMap() {
return checkedNavigableMap(nm.descendingMap(), keyType, valueType);
}
public NavigableSet<K> keySet() {
return navigableKeySet();
}
public NavigableSet<K> navigableKeySet() {
return checkedNavigableSet(nm.navigableKeySet(), keyType);
}
public NavigableSet<K> descendingKeySet() {
return checkedNavigableSet(nm.descendingKeySet(), keyType);
}
@Override
public NavigableMap<K,V> subMap(K fromKey, K toKey) {
return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false),
keyType, valueType);
}
@Override
public NavigableMap<K,V> headMap(K toKey) {
return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType);
}
@Override
public NavigableMap<K,V> tailMap(K fromKey) {
return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType);
}
public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType);
}
public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType);
}
public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType);
}
}
// Empty collections
/**
* 返回没有元素的迭代器。更准确地说，{@link Iterator＃hasNext hasNext}始终返回{@code false}。
* {@link Iterator＃next next}总是抛出{@link NoSuchElementException}。
* {@link Iterator＃remove remove}总是抛出{@link IllegalStateException}。
* 允许（但不是必需）此方法的实现，以通过多次调用返回相同的对象。
*/
@SuppressWarnings("unchecked")
public static <T> Iterator<T> emptyIterator() {
return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
}
private static class EmptyIterator<E> implements Iterator<E> {
static final EmptyIterator<Object> EMPTY_ITERATOR
= new EmptyIterator<>();
public boolean hasNext() { return false; }
public E next() { throw new NoSuchElementException(); }
public void remove() { throw new IllegalStateException(); }
@Override
public void forEachRemaining(Consumer<? super E> action) {
Objects.requireNonNull(action);
}
}
@SuppressWarnings("unchecked")
public static <T> ListIterator<T> emptyListIterator() {
return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
}
private static class EmptyListIterator<E>
extends EmptyIterator<E>
implements ListIterator<E>
{
static final EmptyListIterator<Object> EMPTY_ITERATOR
= new EmptyListIterator<>();
public boolean hasPrevious() { return false; }
public E previous() { throw new NoSuchElementException(); }
public int nextIndex() { return 0; }
public int previousIndex() { return -1; }
public void set(E e) { throw new IllegalStateException(); }
public void add(E e) { throw new UnsupportedOperationException(); }
}
/**
* 返回没有元素的枚举。更准确地说，{@link Enumeration＃hasMoreElements hasMoreElements}始终返回{@code false}。
* {@link Enumeration＃nextElement nextElement}总是抛出{@link NoSuchElementException}。
* 允许（但不是必需）此方法的实现，以通过多次调用返回相同的对象。
*/
@SuppressWarnings("unchecked")
public static <T> Enumeration<T> emptyEnumeration() {
return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
}
private static class EmptyEnumeration<E> implements Enumeration<E> {
static final EmptyEnumeration<Object> EMPTY_ENUMERATION
= new EmptyEnumeration<>();
public boolean hasMoreElements() { return false; }
public E nextElement() { throw new NoSuchElementException(); }
}
/**
* The empty set (immutable). This set is serializable.
*
* @see
*/
@SuppressWarnings("rawtypes")
public static final Set EMPTY_SET = new EmptySet<>();
@SuppressWarnings("unchecked")
public static final <T> Set<T> emptySet() {
return (Set<T>) EMPTY_SET;
}
private static class EmptySet<E>
extends AbstractSet<E>
implements Serializable
{
private static final long serialVersionUID = 1582296315990362920L;
public Iterator<E> iterator() { return emptyIterator(); }
public int size() {return 0;}
public boolean isEmpty() {return true;}
public boolean contains(Object obj) {return false;}
public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
public Object[] toArray() { return new Object[0]; }
public <T> T[] toArray(T[] a) {
if (a.length > 0)
a[0] = null;
return a;
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {
Objects.requireNonNull(action);
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
return false;
}
@Override
public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
// Preserves singleton property
private Object readResolve() {
return EMPTY_SET;
}
}
@SuppressWarnings("unchecked")
public static <E> SortedSet<E> emptySortedSet() {
return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
}
@SuppressWarnings("unchecked")
public static <E> NavigableSet<E> emptyNavigableSet() {
return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
}
@SuppressWarnings("rawtypes")
public static final List EMPTY_LIST = new EmptyList<>();
@SuppressWarnings("unchecked")
public static final <T> List<T> emptyList() {
return (List<T>) EMPTY_LIST;
}
/**
* @serial include
*/
private static class EmptyList<E>
extends AbstractList<E>
implements RandomAccess, Serializable {
private static final long serialVersionUID = 8842843931221139166L;
public Iterator<E> iterator() {
return emptyIterator();
}
public ListIterator<E> listIterator() {
return emptyListIterator();
}
public int size() {return 0;}
public boolean isEmpty() {return true;}
public boolean contains(Object obj) {return false;}
public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
public Object[] toArray() { return new Object[0]; }
public <T> T[] toArray(T[] a) {
if (a.length > 0)
a[0] = null;
return a;
}
public E get(int index) {
throw new IndexOutOfBoundsException("Index: "+index);
}
public boolean equals(Object o) {
return (o instanceof List) && ((List<?>)o).isEmpty();
}
public int hashCode() { return 1; }
@Override
public boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
return false;
}
@Override
public void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
}
@Override
public void sort(Comparator<? super E> c) {
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {
Objects.requireNonNull(action);
}
@Override
public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
// Preserves singleton property
private Object readResolve() {
return EMPTY_LIST;
}
}
@SuppressWarnings("rawtypes")
public static final Map EMPTY_MAP = new EmptyMap<>();
@SuppressWarnings("unchecked")
public static final <K,V> Map<K,V> emptyMap() {
return (Map<K,V>) EMPTY_MAP;
}
@SuppressWarnings("unchecked")
public static final <K,V> SortedMap<K,V> emptySortedMap() {
return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
}
@SuppressWarnings("unchecked")
public static final <K,V> NavigableMap<K,V> emptyNavigableMap() {
return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
}
/**
* @serial include
*/
private static class EmptyMap<K,V>
extends AbstractMap<K,V>
implements Serializable
{
private static final long serialVersionUID = 6428348081105594320L;
public int size() {return 0;}
public boolean isEmpty() {return true;}
public boolean containsKey(Object key) {return false;}
public boolean containsValue(Object value) {return false;}
public V get(Object key) {return null;}
public Set<K> keySet() {return emptySet();}
public Collection<V> values() {return emptySet();}
public Set<Map.Entry<K,V>> entrySet() {return emptySet();}
public boolean equals(Object o) {
return (o instanceof Map) && ((Map<?,?>)o).isEmpty();
}
public int hashCode() {return 0;}
// Override default methods in Map
@Override
@SuppressWarnings("unchecked")
public V getOrDefault(Object k, V defaultValue) {
return defaultValue;
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
Objects.requireNonNull(action);
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
Objects.requireNonNull(function);
}
@Override
public V putIfAbsent(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
throw new UnsupportedOperationException();
}
@Override
public V replace(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
// Preserves singleton property
private Object readResolve() {
return EMPTY_MAP;
}
}
// Singleton collections
/**
* 返回仅包含指定对象的不可变集合。返回的集合是可序列化的。
*/
public static <T> Set<T> singleton(T o) {
return new SingletonSet<>(o);
}
static <E> Iterator<E> singletonIterator(final E e) {
return new Iterator<E>() {
private boolean hasNext = true;
public boolean hasNext() {
return hasNext;
}
public E next() {
if (hasNext) {
hasNext = false;
return e;
}
throw new NoSuchElementException();
}
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
Objects.requireNonNull(action);
if (hasNext) {
action.accept(e);
hasNext = false;
}
}
};
}
static <T> Spliterator<T> singletonSpliterator(final T element) {
return new Spliterator<T>() {
long est = 1;
@Override
public Spliterator<T> trySplit() {
return null;
}
@Override
public boolean tryAdvance(Consumer<? super T> consumer) {
Objects.requireNonNull(consumer);
if (est > 0) {
est--;
consumer.accept(element);
return true;
}
return false;
}
@Override
public void forEachRemaining(Consumer<? super T> consumer) {
tryAdvance(consumer);
}
@Override
public long estimateSize() {
return est;
}
@Override
public int characteristics() {
int value = (element != null) ? Spliterator.NONNULL : 0;
return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE |
Spliterator.DISTINCT | Spliterator.ORDERED;
}
};
}
/**
* @serial include
*/
private static class SingletonSet<E>
extends AbstractSet<E>
implements Serializable
{
private static final long serialVersionUID = 3193687207550431679L;
private final E element;
SingletonSet(E e) {element = e;}
public Iterator<E> iterator() {
return singletonIterator(element);
}
public int size() {return 1;}
public boolean contains(Object o) {return eq(o, element);}
// Override default methods for Collection
@Override
public void forEach(Consumer<? super E> action) {
action.accept(element);
}
@Override
public Spliterator<E> spliterator() {
return singletonSpliterator(element);
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
throw new UnsupportedOperationException();
}
}
/**
* 返回仅包含指定对象的不可变列表。返回的列表是可序列化的。
*/
public static <T> List<T> singletonList(T o) {
return new SingletonList<>(o);
}
/**
* @serial include
*/
private static class SingletonList<E>
extends AbstractList<E>
implements RandomAccess, Serializable {
private static final long serialVersionUID = 3093736618740652951L;
private final E element;
SingletonList(E obj) {element = obj;}
public Iterator<E> iterator() {
return singletonIterator(element);
}
public int size() {return 1;}
public boolean contains(Object obj) {return eq(obj, element);}
public E get(int index) {
if (index != 0)
throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
return element;
}
// Override default methods for Collection
@Override
public void forEach(Consumer<? super E> action) {
action.accept(element);
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
throw new UnsupportedOperationException();
}
@Override
public void replaceAll(UnaryOperator<E> operator) {
throw new UnsupportedOperationException();
}
@Override
public void sort(Comparator<? super E> c) {
}
@Override
public Spliterator<E> spliterator() {
return singletonSpliterator(element);
}
}
public static <K,V> Map<K,V> singletonMap(K key, V value) {
return new SingletonMap<>(key, value);
}
/**
* @serial include
*/
private static class SingletonMap<K,V>
extends AbstractMap<K,V>
implements Serializable {
private static final long serialVersionUID = -6979724477215052911L;
private final K k;
private final V v;
SingletonMap(K key, V value) {
k = key;
v = value;
}
public int size() {return 1;}
public boolean isEmpty() {return false;}
public boolean containsKey(Object key) {return eq(key, k);}
public boolean containsValue(Object value) {return eq(value, v);}
public V get(Object key) {return (eq(key, k) ? v : null);}
private transient Set<K> keySet;
private transient Set<Map.Entry<K,V>> entrySet;
private transient Collection<V> values;
public Set<K> keySet() {
if (keySet==null)
keySet = singleton(k);
return keySet;
}
public Set<Map.Entry<K,V>> entrySet() {
if (entrySet==null)
entrySet = Collections.<Map.Entry<K,V>>singleton(
new SimpleImmutableEntry<>(k, v));
return entrySet;
}
public Collection<V> values() {
if (values==null)
values = singleton(v);
return values;
}
// Override default methods in Map
@Override
public V getOrDefault(Object key, V defaultValue) {
return eq(key, k) ? v : defaultValue;
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
action.accept(k, v);
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
throw new UnsupportedOperationException();
}
@Override
public V putIfAbsent(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
throw new UnsupportedOperationException();
}
@Override
public V replace(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
}
// Miscellaneous
/**
* 返回由指定对象的n个副本组成的不可变列表。
* 新分配的数据对象很小（它包含对数据对象的单个引用）。
* 该方法与List.addAll方法结合使用以增长列表很有用。
* 返回的列表是可序列化的。
*/
public static <T> List<T> nCopies(int n, T o) {
if (n < 0)
throw new IllegalArgumentException("List length = " + n);
return new CopiesList<>(n, o);
}
/**
* @serial include
*/
private static class CopiesList<E>
extends AbstractList<E>
implements RandomAccess, Serializable
{
private static final long serialVersionUID = 2739099268398711800L;
final int n;
final E element;
CopiesList(int n, E e) {
assert n >= 0;
this.n = n;
element = e;
}
public int size() {
return n;
}
public boolean contains(Object obj) {
return n != 0 && eq(obj, element);
}
public int indexOf(Object o) {
return contains(o) ? 0 : -1;
}
public int lastIndexOf(Object o) {
return contains(o) ? n - 1 : -1;
}
public E get(int index) {
if (index < 0 || index >= n)
throw new IndexOutOfBoundsException("Index: "+index+
", Size: "+n);
return element;
}
public Object[] toArray() {
final Object[] a = new Object[n];
if (element != null)
Arrays.fill(a, 0, n, element);
return a;
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
final int n = this.n;
if (a.length < n) {
a = (T[])java.lang.reflect.Array
.newInstance(a.getClass().getComponentType(), n);
if (element != null)
Arrays.fill(a, 0, n, element);
} else {
Arrays.fill(a, 0, n, element);
if (a.length > n)
a[n] = null;
}
return a;
}
public List<E> subList(int fromIndex, int toIndex) {
if (fromIndex < 0)
throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
if (toIndex > n)
throw new IndexOutOfBoundsException("toIndex = " + toIndex);
if (fromIndex > toIndex)
throw new IllegalArgumentException("fromIndex(" + fromIndex +
") > toIndex(" + toIndex + ")");
return new CopiesList<>(toIndex - fromIndex, element);
}
// Override default methods in Collection
@Override
public Stream<E> stream() {
return IntStream.range(0, n).mapToObj(i -> element);
}
@Override
public Stream<E> parallelStream() {
return IntStream.range(0, n).parallel().mapToObj(i -> element);
}
@Override
public Spliterator<E> spliterator() {
return stream().spliterator();
}
}
@SuppressWarnings("unchecked")
public static <T> Comparator<T> reverseOrder() {
return (Comparator<T>) ReverseComparator.REVERSE_ORDER;
}
/**
* @serial include
*/
private static class ReverseComparator
implements Comparator<Comparable<Object>>, Serializable {
private static final long serialVersionUID = 7207038068494060240L;
static final ReverseComparator REVERSE_ORDER
= new ReverseComparator();
public int compare(Comparable<Object> c1, Comparable<Object> c2) {
return c2.compareTo(c1);
}
private Object readResolve() { return Collections.reverseOrder(); }
@Override
public Comparator<Comparable<Object>> reversed() {
return Comparator.naturalOrder();
}
}
public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
if (cmp == null)
return reverseOrder();
if (cmp instanceof ReverseComparator2)
return ((ReverseComparator2<T>)cmp).cmp;
return new ReverseComparator2<>(cmp);
}
/**
* @serial include
*/
private static class ReverseComparator2<T> implements Comparator<T>,
Serializable
{
private static final long serialVersionUID = 4374092139857L;
/**
* The comparator specified in the static factory. This will never
* be null, as the static factory returns a ReverseComparator
* instance if its argument is null.
*
* @serial
*/
final Comparator<T> cmp;
ReverseComparator2(Comparator<T> cmp) {
assert cmp != null;
this.cmp = cmp;
}
public int compare(T t1, T t2) {
return cmp.compare(t2, t1);
}
public boolean equals(Object o) {
return (o == this) ||
(o instanceof ReverseComparator2 &&
cmp.equals(((ReverseComparator2)o).cmp));
}
public int hashCode() {
return cmp.hashCode() ^ Integer.MIN_VALUE;
}
@Override
public Comparator<T> reversed() {
return cmp;
}
}
/**
* 返回指定集合的枚举。这提供了与需要枚举作为输入的旧式API的互操作性。
*/
public static <T> Enumeration<T> enumeration(final Collection<T> c) {
return new Enumeration<T>() {
private final Iterator<T> i = c.iterator();
public boolean hasMoreElements() {
return i.hasNext();
}
public T nextElement() {
return i.next();
}
};
}
public static <T> ArrayList<T> list(Enumeration<T> e) {
ArrayList<T> l = new ArrayList<>();
while (e.hasMoreElements())
l.add(e.nextElement());
return l;
}
static boolean eq(Object o1, Object o2) {
return o1==null ? o2==null : o1.equals(o2);
}
/**
* 返回指定集合中等于指定对象的元素数。
* 更正式地，返回集合中元素e的数量，使得（o == null？e == null：o.equals（e））。
*/
public static int frequency(Collection<?> c, Object o) {
int result = 0;
if (o == null) {
for (Object e : c)
if (e == null)
result++;
} else {
for (Object e : c)
if (o.equals(e))
result++;
}
return result;
}
/**
* 如果两个指定的集合没有共同的元素，则返回{@code true}。
* 如果对不符合{@code Collection}的一般合同的馆藏使用此方法，则必须格外小心。
* 实现可以选择对一个集合进行迭代并测试是否包含在另一个集合中（或执行任何等效的计算）。
* 如果两个集合都使用非标准的相等性测试（{@link SortedSet}的顺序与等号不兼容，
* 或者{@link IdentityHashMap}的键集也是如此），则两个集合都必须使用相同的非标准的相等性测试，或者该方法的结果是不确定的。
* 使用集合中可能包含的元素有限制的集合时，也必须格外小心。
* 允许集合实现对涉及其认为不合格的元素的任何操作引发异常。
* 为了绝对安全，指定的集合应仅包含两个集合均符合条件的元素。
* 请注意，允许在两个参数中传递相同的集合，在这种情况下，当且仅当集合为空时，该方法才返回{@code true}。
*/
public static boolean disjoint(Collection<?> c1, Collection<?> c2) {
Collection<?> contains = c2;
Collection<?> iterate = c1;
if (c1 instanceof Set) {
iterate = c2;
contains = c1;
} else if (!(c2 instanceof Set)) {
int c1size = c1.size();
int c2size = c2.size();
if (c1size == 0 || c2size == 0) {
// At least one collection is empty. Nothing will match.
return true;
}
if (c1size > c2size) {
iterate = c2;
contains = c1;
}
}
for (Object e : iterate) {
if (contains.contains(e)) {
// Found a common element. Collections are not disjoint.
return false;
}
}
return true;
}
/**
* 将所有指定的元素添加到指定的集合中。
* 要添加的元素可以单独指定或作为数组指定。
* 此便捷方法的行为与c.addAll（Arrays.asList（elements））的行为相同，
* 但是在大多数实现下，此方法的运行速度可能明显更快。
* 当分别指定元素时，此方法提供了一种向现有集合中添加一些元素的便捷方法：
* Collections.addAll（flavors，“ Peachesn Plutonium”，“ Rocky Racoon”）;
*
*/
@SafeVarargs
public static <T> boolean addAll(Collection<? super T> c, T... elements) {
boolean result = false;
for (T element : elements)
result |= c.add(element);
return result;
}
/**
* 返回指定地图支持的集合。
* 结果集显示的排序，并发性和性能特征与支持映射相同。
* 本质上，此工厂方法提供了与任何{@link Map}实现相对应的{@link Set}实现。
* 无需在已经具有相应的{@link Set}实现的{@link Map}实现（例如{@link HashMap}
* 或{@link TreeMap}）上使用此方法。
* 此方法返回的集合上的每个方法调用都会在后备映射或其keySet视图上导致一个方法调用，只有一个例外。
* addAll方法被实现为在支持映射上的一系列put调用。
* 调用此方法时，指定的映射必须为空，并且在此方法返回后不能直接访问。
* 如果将映射创建为空，将其直接传递给此方法，并且不保留对该映射的引用，则可以确保满足这些条件，
* 如以下代码片段所示：
* Set <Object> weakHashSet = Collections.newSetFromMap（new WeakHashMap <Object，Boolean >（））;
*
*/
public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
return new SetFromMap<>(map);
}
/**
* @serial include
*/
private static class SetFromMap<E> extends AbstractSet<E>
implements Set<E>, Serializable
{
private final Map<E, Boolean> m; // The backing map
private transient Set<E> s; // Its keySet
SetFromMap(Map<E, Boolean> map) {
if (!map.isEmpty())
throw new IllegalArgumentException("Map is non-empty");
m = map;
s = map.keySet();
}
public void clear() { m.clear(); }
public int size() { return m.size(); }
public boolean isEmpty() { return m.isEmpty(); }
public boolean contains(Object o) { return m.containsKey(o); }
public boolean remove(Object o) { return m.remove(o) != null; }
public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
public Iterator<E> iterator() { return s.iterator(); }
public Object[] toArray() { return s.toArray(); }
public <T> T[] toArray(T[] a) { return s.toArray(a); }
public String toString() { return s.toString(); }
public int hashCode() { return s.hashCode(); }
public boolean equals(Object o) { return o == this || s.equals(o); }
public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
// addAll is the only inherited implementation
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {
s.forEach(action);
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
return s.removeIf(filter);
}
@Override
public Spliterator<E> spliterator() {return s.spliterator();}
@Override
public Stream<E> stream() {return s.stream();}
@Override
public Stream<E> parallelStream() {return s.parallelStream();}
private static final long serialVersionUID = 2454657854757543876L;
private void readObject(java.io.ObjectInputStream stream)
throws IOException, ClassNotFoundException
{
stream.defaultReadObject();
s = m.keySet();
}
}
/**
* 返回{@link Deque}作为后进先出（Lifo）{@link Queue}的视图。
* 方法add映射为push，remove映射为pop等。
* 当您想使用需要Queue但需要Lifo排序的方法时，此视图很有用。
* 此方法返回的队列上的每个方法调用都会在后备双端队列上恰好产生一个方法调用，但有一个例外。
* {@link Queue＃addAll addAll}方法实现为对后备双端队列的{@link Deque＃addFirst addFirst}调用序列。
*
* @param <T> the class of the objects in the deque
* @param deque the deque
* @return the queue
* @since 1.6
*/
public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
return new AsLIFOQueue<>(deque);
}
/**
* @serial include
*/
static class AsLIFOQueue<E> extends AbstractQueue<E>
implements Queue<E>, Serializable {
private static final long serialVersionUID = 1802017725587941708L;
private final Deque<E> q;
AsLIFOQueue(Deque<E> q) { this.q = q; }
public boolean add(E e) { q.addFirst(e); return true; }
public boolean offer(E e) { return q.offerFirst(e); }
public E poll() { return q.pollFirst(); }
public E remove() { return q.removeFirst(); }
public E peek() { return q.peekFirst(); }
public E element() { return q.getFirst(); }
public void clear() { q.clear(); }
public int size() { return q.size(); }
public boolean isEmpty() { return q.isEmpty(); }
public boolean contains(Object o) { return q.contains(o); }
public boolean remove(Object o) { return q.remove(o); }
public Iterator<E> iterator() { return q.iterator(); }
public Object[] toArray() { return q.toArray(); }
public <T> T[] toArray(T[] a) { return q.toArray(a); }
public String toString() { return q.toString(); }
public boolean containsAll(Collection<?> c) {return q.containsAll(c);}
public boolean removeAll(Collection<?> c) {return q.removeAll(c);}
public boolean retainAll(Collection<?> c) {return q.retainAll(c);}
// We use inherited addAll; forwarding addAll would be wrong
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {q.forEach(action);}
@Override
public boolean removeIf(Predicate<? super E> filter) {
return q.removeIf(filter);
}
@Override
public Spliterator<E> spliterator() {return q.spliterator();}
@Override
public Stream<E> stream() {return q.stream();}
@Override
public Stream<E> parallelStream() {return q.parallelStream();}
}
}
问题记录
