lambda - 方法引用

方法引用是一种更为简洁的代码构造，它可以让你直接引用已有Java类的方法或者构造器，你可以通过使用::关键字来引用一个方法。

方法引用可以分为以下三种：

• 静态方法引用
• 实例方法引用
• 构造函数引用

下面是一些示例代码：

// 静态方法引用
Function<String, Integer> function = Integer::parseInt;
Integer result = function.apply("123");
System.out.println(result); // 输出：123


// 实例方法引用
String test = "Hello, World!";
Supplier<Integer> supplier = test::length;
int length = supplier.get();
System.out.println(length); // 输出：13


// 构造函数引用
Supplier<Test> supplier = Test::new;
Test test = supplier.get();

日常应用

package com.sea.bean;

@FunctionalInterface
interface ClickListenner<T> {
    void onclick(T a);
}

class Receiver {
    public void doclick(String msg) {
        System.out.println(msg);
    }
}

class Provider {
    private ClickListenner<String> listenner;

    public Provider(ClickListenner<String> listenner) {
        this.listenner = listenner;
    }

    public void sendMessage() {
        listenner.onclick("click...");
    }
}

public class TestA {
    public static void main(String[] args) {
        {
            //原始写法
            Receiver receiver = new Receiver();
            Provider provider = new Provider(new ClickListenner<String>() {

                @Override
                public void onclick(String msg) {
                    receiver.doclick(msg);
                }
            });
            provider.sendMessage();
        }
        {
            // Lambda下的简写
            Receiver receiver = new Receiver();
            Provider provider = new Provider((msg) -> {
                receiver.doclick(msg);
            });
            provider.sendMessage();
        }
        {
            // Lambda下的极简写法
            Receiver receiver = new Receiver();
            Provider provider = new Provider(receiver::doclick);
            provider.sendMessage();
        }
    }
}