1 package com.test; 2  3 @FunctionalInterface 4 interface AddDo 5 { 6     int doAdd(int a, int b); 7 } 8  9 class Math10 {11     public AddDo addDo;12 13     public Math(AddDo addDo)14     {15         this.addDo = addDo;16     }17 18     public int add(int a, int b)19     {20         return this.addDo.doAdd(a, b);21     }22 }23 24 public class Java8LambdaTest25 {26     // 1. lambda表达式支持27     public static void lambdaSupport()28     {29         System.out.println("------ lambda表达式方式 ---------");30         Math math = new Math((a, b) ->31         {32             return a + b;33         });34         System.out.println(math.add(3, 5));35         36         System.out.println("------ 静态方法引用方式 ---------");37         Math math2 = new Math(Java8LambdaTest::staticHelper);38         System.out.println(math2.add(3, 5));39         40         System.out.println("------ 实例方法引用方式 ---------");41         Math math3 = new Math(new Java8LambdaTest()::instanceHelper);42         System.out.println(math3.add(3, 5));43         44         //构造方法引用方式为Java8LambdaTest::new45     }46     public static void main(String[] args)47     {48         lambdaSupport();49     }50     public static int staticHelper(int a, int b)51     {52         System.out.println("do staticHelper()");53         System.out.println("a: " + a + ", b: " + b);54         return a + b;55     }56     public int instanceHelper(int a, int b)57     {58         System.out.println("do helper()");59         System.out.println("a: " + a + ", b: " + b);60         return a + b;61     }62 }

 

2. 接口可以添加默认或者静态(两者只能存在一个修饰符)方法，但是接口仍然不能实例化，不能含有static代码块

1 package com.test; 2  3 interface MathOpt 4 { 5     default int add(int a, int b) 6     { 7         return a + b; 8     } 9     10     static int subtract(int a, int b)11     {12         return a - b;13     }14 }15 16 public class Java8InterfaceDefaultMethod17 {18     public static void main(String[] args)19     {20         System.out.println(MathOpt.subtract(3, 5));21     }22 }