Guava工具类

1、导入依赖

<dependency>
	<groupId>com.google.guava</groupId>
		<artifactId>guava</artifactId>
		<version>17.0</version>
</dependency>

2、创建集合

List<String> list = Lists.newArrayList();
Set<String> set = Sets.newHashSet();
Map<String, String> map = Maps.newHashMap();

3、将集合转换为特定规则的字符串

List<String> list = new ArrayList<String>();
list.add("aa");
list.add("bb");
list.add("cc");
String result = Joiner.on("-").join(list);
//result为  aa-bb-cc

4、将String转换为特定的集合

String str = "1-2-3-4-5-6";
List<String> list = Splitter.on("-").splitToList(str);
//list为  [1, 2, 3, 4, 5, 6]

5、set的交集, 并集, 差集

HashSet setA = newHashSet(1, 2, 3, 4, 5);  
HashSet setB = newHashSet(4, 5, 6, 7, 8);  
   
SetView union = Sets.union(setA, setB);    
System.out.println("union:");  
for (Integer integer : union)  
    System.out.println(integer);           //union 并集:12345867
   
SetView difference = Sets.difference(setA, setB);  
System.out.println("difference:");  
for (Integer integer : difference)  
    System.out.println(integer);        //difference 差集:123
   
SetView intersection = Sets.intersection(setA, setB);  
System.out.println("intersection:");  
for (Integer integer : intersection)  
    System.out.println(integer);  //intersection 交集:45

6、map的交集，并集，差集

HashMap<String, Integer> mapA = Maps.newHashMap();
mapA.put("a", 1);mapA.put("b", 2);mapA.put("c", 3);

HashMap<String, Integer> mapB = Maps.newHashMap();
mapB.put("b", 20);mapB.put("c", 3);mapB.put("d", 4);

MapDifference differenceMap = Maps.difference(mapA, mapB);
differenceMap.areEqual();
Map entriesDiffering = differenceMap.entriesDiffering();
Map entriesOnlyLeft = differenceMap.entriesOnlyOnLeft();
Map entriesOnlyRight = differenceMap.entriesOnlyOnRight();
Map entriesInCommon = differenceMap.entriesInCommon();

System.out.println(entriesDiffering);   // {b=(2, 20)}
System.out.println(entriesOnlyLeft);    // {a=1}
System.out.println(entriesOnlyRight);   // {d=4}
System.out.println(entriesInCommon);    // {c=3}