java多线程四种实现方法

Posted 2021-02-10 惬意的小屋

package com.zrun.TestThread;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class App {
    public static void main(String[] args) throws Exception, ExecutionException {
        System.out.println("主线程启动:"
                + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
                        .format(new Date()));

        // 方式1
        // ThreadEx thread1 = new ThreadEx();
        // thread1.start();
        // Thread.sleep(2000);
        // System.out.println("主线程执行结束:"
        // + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
        // .format(new Date()));

        // 方式2
        // Thread thread2 = new Thread(new RunableEx());
        // thread2.start();
        // Thread.sleep(2000);
        // System.out.println("主线程执行结束:"
        // + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
        // .format(new Date()));

        // 方式3
        // Callable<Object> oneCallable = new Thread3<Object>();
        // FutureTask<Object> oneTask = new FutureTask<Object>(oneCallable);
        // Thread t = new Thread(oneTask);
        // t.start();
        // Thread.sleep(2000);
        // System.out.println("主线程执行结束:"
        // + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
        // .format(new Date()));
        // // 主线程执行的2秒钟之后，子线程只要再过3秒就结束了，从而得到子线程的结果；这里get方法会阻塞主线程
        // System.out.println(oneTask.get().toString());

        // 方式4
        Thread4.test();
        Thread.sleep(2000);
        System.out.println("主线程执行结束:"
                + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
                        .format(new Date()));
    }
}

// 方式1：继承Thread类
class ThreadEx extends Thread {
    @Override
    public void run() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("子线程执行结束:"
                + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
                        .format(new Date()));
    }
}

// 方式2：实现Runnable接口
class RunableEx implements Runnable {
    public void run() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("子线程执行结束:"
                + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
                        .format(new Date()));
    }
}

// 方式3：通过Callable和FutureTask；这种方式可以拿到子线程的返回值
class Thread3<Object> implements Callable<Object> {

    @Override
    public Object call() throws Exception {
        Thread.sleep(5000);
        return (Object) ("我是子线程的返回值:" + new SimpleDateFormat(
                "yyyy-MM-dd HH:mm:ss").format(new Date()));
    }
}

// 方式4：通过线程池创建线程
class Thread4 {
    static int POOL_NUM = 5;

    public static void test() {
        ExecutorService executorService = Executors.newFixedThreadPool(5);
        for (int i = 0; i < POOL_NUM; i++) {
            RunableEx thread = new RunableEx();
            executorService.execute(thread);
        }
        // 关闭线程池
        executorService.shutdown();
    }
}