java8新特性

 1 package com.test;

@FunctionalInterface
interface AddDo
{
    int doAdd(int a, int b);
}

class Math
{
    public AddDo addDo;

    public Math(AddDo addDo)
    {
        this.addDo = addDo;
    }

    public int add(int a, int b)
    {
        return this.addDo.doAdd(a, b);
    }
}

public class Java8LambdaTest
{
    // 1. lambda表达式支持
    public static void lambdaSupport()
    {
        System.out.println("------ lambda表达式方式 ---------");
        Math math = new Math((a, b) ->
        {
            return a + b;
        });
        System.out.println(math.add(3, 5));
        
        System.out.println("------ 静态方法引用方式 ---------");
        Math math2 = new Math(Java8LambdaTest::staticHelper);
        System.out.println(math2.add(3, 5));
        
        System.out.println("------ 实例方法引用方式 ---------");
        Math math3 = new Math(new Java8LambdaTest()::instanceHelper);
        System.out.println(math3.add(3, 5));
        
        //构造方法引用方式为Java8LambdaTest::new
    }
    public static void main(String[] args)
    {
        lambdaSupport();
    }
    public static int staticHelper(int a, int b)
    {
        System.out.println("do staticHelper()");
        System.out.println("a: " + a + ", b: " + b);
        return a + b;
    }
    public int instanceHelper(int a, int b)
    {
        System.out.println("do helper()");
        System.out.println("a: " + a + ", b: " + b);
        return a + b;
    }
}

 

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

package com.test;

interface MathOpt
{
    default int add(int a, int b)
    {
        return a + b;
    }
    
    static int subtract(int a, int b)
    {
        return a - b;
    }
}

public class Java8InterfaceDefaultMethod
{
    public static void main(String[] args)
    {
        System.out.println(MathOpt.subtract(3, 5));
    }
}