java8的lambda表达式：使得代码更加紧凑；修改方法的能力；更好的支持多核处理（并行处理函数和filter\map\reduce）

例子1:

java7中，list集合排序：

public static void testJava7SortList() {        List
     
       names = Arrays.asList("peter", "anna", "mike", "xenia");        Collections.sort(names, new Comparator
      
       () {            @Override            public int compare(String a, String b) {                return b.compareTo(a);            }        });        System.out.println(names);    }
      
     

java8中，list集合排序：

 

public static void testJava8SortList1() {        List
     
       names = Arrays.asList("peter", "anna", "mike", "xenia");        Collections.sort(names, (String a, String b) -> {            return b.compareTo(a);        });        System.out.println(names);    }    public static void testJava8SortList2() {        List
      
        names = Arrays.asList("peter", "anna", "mike", "xenia");        Collections.sort(names, (String a, String b) -> b.compareTo(a));        System.out.println(names);    }    // 只要一行代码，包含了方法体。你甚至可以连大括号对{}和return关键字都省略不要。不过这还不是最短的写法    // Java编译器能够自动识别参数的类型，所以你就可以省略掉类型不写    public static void testJava8SortList3() {        List
       
         names = Arrays.asList("peter", "anna", "mike", "xenia");        Collections.sort(names, (a, b) -> b.compareTo(a));        System.out.println(names);    }
       
      
     

 

例子2:

Thread的处理：

public static void testJava8Thread() {        // Java 7：        new Thread(new Runnable() {            @Override            public void run() {                System.out.println("java7 thread");            }        }).start();        // Java 8方式：        new Thread(() -> System.out.println("java8 thread")).start();        try {            Thread.sleep(1000L);        } catch (InterruptedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }

例子3:

迭代处理：

public static void testForEach() {        // Java 7：        List
     
       features1 = Arrays.asList("a", "b", "c", "d");        for (String feature : features1) {            System.out.println(feature);        }        // Java 8：        List
      
        features2 = Arrays.asList("a", "b", "c", "d");        features2.forEach(n -> System.out.println(n));        // 使用Java 8的方法引用更方便，方法引用由::双冒号操作符标示，        // 看起来像C++的作用域解析运算符        features2.forEach(System.out::println);    }
      
     

 

例子4:

labmda表达式和函数试接口：

java.util.function。它包含了很多类，用来支持Java的函数式编程。其中一个便是Predicate，使用 java.util.function.Predicate 函数式接口以及lambda表达式，可以向API方法添加逻辑，用更少的代码支持更多的动态行为。

public static void testLambdaFilter() {        List
     
       languages = Arrays.asList("Java", "Scala", "C++", "Haskell", "Lisp");                 //查询J开头的字符串        System.out.println("Languages which starts with J :");        filter(languages, (str)->str.startsWith("J"));             //查询出所有        System.out.println("Print all languages :");        filter(languages, (str)->true);    }        public static void filter(List
      
        names, Predicate
       
         condition) {        for(String name: names)  {            if(condition.test(name)) {                System.out.println(name + " ");            }        }    }    public static void filter2(List
        
          names, Predicate
         
           condition) {        names.stream().filter((name) -> (condition.test(name))).forEach((name) -> {            System.out.println(name + " ");        });    }
         
        
       
      
     

例子5:

 函数式编程概念map

// 为每个订单加上12%的税// 老方法：List costBeforeTax = Arrays.asList(100, 200, 300, 400, 500);double total = 0;for (Integer cost : costBeforeTax) {    double price = cost + .12*cost;    total = total + price;}System.out.println("Total : " + total); // 新方法：List costBeforeTax = Arrays.asList(100, 200, 300, 400, 500);double bill = costBeforeTax.stream().map((cost) -> cost + .12*cost).reduce((sum, cost) -> sum + cost).get();System.out.println("Total : " + bill);