Simple Lambda Sample

例1 用lambda表达式实现Runnable

 public static void main(String[] args) {
    Runnable runnable = () -> System.out.println("This is Lambda Test!");
    Thread thread = new Thread(runnable);
    thread.start();
} 

例2 使用Java 8 lambda表达式进行事件处理

 public static void main(String[] args) {
    JButton show = new JButton("Show");
    show.addActionListener((e) -> {
        System.out.println("This is Lambda Sample For Action");
    });
}

例3 使用lambda表达式对列表进行迭代

 public static void main(String[] args) {
    List<String> features = Arrays.asList("Lambdas", "Default Method", "Stream API", "Date and Time API");
    features.forEach(n -> System.out.println(n));
}

例4 使用lambda表达式和函数式接口Predicate

 public static void main(String[] args) {
    List<String> languages = Arrays.asList("Java", "Scala", "C++", "Haskell", "Lisp");

    System.out.println("Languages which starts with J :");
    filter(languages, (str)->str.startsWith("J"));

    System.out.println("Languages which ends with a ");
    filter(languages, (str)->str.endsWith("a"));

    System.out.println("Print all languages :");
    filter(languages, (str)->true);

    System.out.println("Print no language : ");
    filter(languages, (str)->false);

    System.out.println("Print language whose length greater than 4:");
    filter(languages, (str)->str.length() > 4);
}

public static void filter(List<String> names, Predicate<String> condition) {
    names.stream().filter(name->condition.test(name)).forEach(name-> System.out.println(name));
}

例5 如何在lambda表达式中加入Predicate

 public static void main(String[] args) {
    List<String> languages = Arrays.asList("Java", "Scala", "Basic", "Haskell", "Lisp");

    Predicate<String> startWithJ = n->n.startsWith("J");
    Predicate<String> fourLengthLetter = n->n.length() == 4;
    languages.stream().filter(startWithJ.and(fourLengthLetter)).forEach(n-> System.out.println("nName, which starts with 'J' and four letter long is : " + n));

    Predicate<String> endWithA = n->n.endsWith("a");
    Predicate<String> fiveLengthLetter = n->n.length() == 5;
    languages.stream().filter(endWithA.or(fiveLengthLetter)).forEach(n-> System.out.println("nName, which end with 'a' or five letter long is : " + n));
}

例6 Java 8中使用lambda表达式的Map和Reduce示例

 public static void main(String[] args) {
    List<Integer> costBeforeTax = Arrays.asList(100, 200, 300, 400);
    costBeforeTax.stream().map(cost->cost + .12*cost).forEach(cost-> System.out.println(cost));

    double bill = costBeforeTax.stream().map(cost->cost + .12*cost).reduce((sum, cost)->sum + cost).get();
    System.out.println("Total:" + bill);
}

例7 通过过滤创建一个String列表

 public static void main(String[] args) {
    List<String> strList = Arrays.asList("abcd", "abcde", "abc", "ab");
    List<String> filtered = strList.stream().filter(x->x.length()>2).collect(Collectors.toList());
    System.out.printf("Original List : %s, filtered list : %s %n", strList, filtered);
}

例8 对列表的每个元素应用函数

 public static void main(String[] args) {
    List<String> G7 = Arrays.asList("USA", "Japan", "France", "Germany", "Italy", "U.K.","Canada");
    String G7Countries = G7.stream().map(x -> x.toUpperCase()).collect(Collectors.joining(", "));
    System.out.println(G7Countries);
}

例9 复制不同的值，创建一个子列表

 public static void main(String[] args) {
    List<Integer> numbers = Arrays.asList(9, 10, 3, 4, 7, 3, 4);
    List<Integer> distinct = numbers.stream().map(i->i*i).distinct().collect(Collectors.toList());
    System.out.printf("Original List : %s,  Square Without duplicates : %s %n", numbers, distinct);
}

例10 计算集合元素的最大值、最小值、总和以及平均值

 public static void main(String[] args) {
    List<Integer> primes = Arrays.asList(2, 3, 5, 7, 11, 13, 17, 19, 23, 29);
    IntSummaryStatistics stats = primes.stream().mapToInt(x->x).summaryStatistics();
    System.out.println("Highest prime number in List : " + stats.getMax());
    System.out.println("Lowest prime number in List : " + stats.getMin());
    System.out.println("Sum of all prime numbers : " + stats.getSum());
    System.out.println("Average of all prime numbers : " + stats.getAverage());
}

附：源码地址