方法引用的基本使用(代码片段)

package com.ly.demo.java8;

/**
 * @author liuyang
 * @create 2020-05-17 23:16
 */
@FunctionalInterface
public interface IntArrayBuilder 
    int[] buildIntArray(int len);

package com.ly.demo.java8;

/**
 * @author liuyang
 * @create 2020-05-17 21:57
 */
// 函数接口,有且仅有一个抽象方法的接口
@FunctionalInterface
public interface MyInterface 
    void print(String str);

package com.ly.demo.java8;

/**
 * @author liuyang
 * @create 2020-05-17 23:00
 */
@FunctionalInterface
public interface MyObjBuilder 
    MyObj build(String name,Integer age);

package com.ly.demo.java8;

/**
 * @author liuyang
 * @create 2020-05-17 21:57
 */
public class MyObj extends MyObjSup 
    public String name;
    public Integer age;

    public MyObj() 
    

    public MyObj(String name, Integer age) 
        this.name = name;
        this.age = age;
    

    public void printStr(MyInterface mi, String str) 
        mi.print(str);
    

    public void printUpperCase(String str) 
        System.out.println(str.toUpperCase());
    

    public static void printLowerCase(String str) 
        System.out.println(str.toLowerCase());
    

    @Override
    public void sayHello(String s) 
        System.out.println("MyObj-你好，我是："+s);
    

    public void say1() 
        // 引用父类的方法
        printStr(super::sayHello,"小明");
    

    public void say2() 
        // 引用本类的方法
        printStr(this::sayHello,"小芳");
    

    MyObj buildMyObj(MyObjBuilder myObjBuilder,String name,Integer age) 
        return myObjBuilder.build(name,age);
    

    int[] createIntArray(int len,IntArrayBuilder iab) 
        return iab.buildIntArray(len);
    

package com.ly.demo.java8;

/**
 * @author liuyang
 * @create 2020-05-17 22:31
 */
public class MyObjSup 
    public void sayHello(String s) 
        System.out.println("MyObjSup-你好，我是："+s);
    

package com.ly.demo.java8;

import org.junit.Test;

/**
 * @author liuyang
 * @create 2020-05-17 22:00
 */
public class MethodRefTest 
    @Test
    public void test1() 
        MyObj myObj = new MyObj();
        // 函数式接口都可以用Lambda表达式代替
        myObj.printStr(s -> System.out.println(s),"hello1");
    

    @Test
    public void test2() 
        MyObj myObj = new MyObj();
        // Lambda表达式也可以用方法引用替代
        // 被引用方法的入参必须和函数式接口方法的入参一致
        myObj.printStr(System.out::println,"hello2");
    

    @Test
    public void test3() 
        MyObj myObj = new MyObj();
        // 引用对象的实例方法
        myObj.printStr(myObj::printUpperCase,"hello3");
    

    @Test
    public void test4() 
        MyObj myObj = new MyObj();
        // 引用类的静态方法
        myObj.printStr(MyObj::printLowerCase,"HELLO4");
    

    @Test
    public void test5() 
        // 测试引用父类的方法
        new MyObj().say1();
    

    @Test
    public void test6() 
        // 测试引用本类的方法
        new MyObj().say2();
    

    @Test
    public void test7() 
        // 测试引用构造方法
        MyObj myObj = new MyObj().buildMyObj(MyObj::new,"liuyang",18);
        System.out.println(myObj.name);
        System.out.println(myObj.age);
    

    @Test
    public void test8() 
        // 测试引用数组的构造方法
        int[] arr = new MyObj().createIntArray(10,int[]::new);
        System.out.println(arr.length);