二、多线程的几种实现方式

多线程三种主要实现方式：继承Thread类，实现Runnable接口、Callable和Futrue。

一、简单实现

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;

public class T02_HowToCreateThread {
    //1.继承Thread类
    static class MyThread extends Thread{
        @Override
        public void run() {
            System.out.println("MyThread-->");
        }
    }
    //3.实现Runnable接口
    static class MyRun implements Runnable{

        @Override
        public void run() {
            System.out.println("MyRunable-->");
        }
    }
    //4.实现Callable接口
    static class MyCall implements Callable{

        @Override
        public Object call() throws Exception {
            System.out.println("myCallable-->");
            return 1;
        }
    }
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        //1.继承Thread类
        new MyThread().start();
        //2.lambda与继承Thread类类//1.继承Thread类似，最简单
        new Thread(()->{
            System.out.println("lambda-->");
        }).start();
        //3.实现Runnable接口
        new Thread(new MyRun()).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("simple->Runnable");
            }
        }).start();
       //4.实现Callable接口,并用包装器FutureTask来同时实现Runable、Callable两个接口,可带返回结果
        MyCall mycall = new MyCall();
        FutureTask futureTask = new FutureTask(mycall);
        new Thread(futureTask).start();
        System.out.println(futureTask.get());
    }
}

二、使用ExecutorService、Callable和Future一起实现带返回值

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

/**
 * 使用ExecutorsService、Callable、Future来实现多个带返回值的线程
 */
public class T02_HowToCreateThread02 {
    static class MyCallable implements Callable{
        private int taskNum;

        public MyCallable(int taskNum){
            this.taskNum = taskNum;
        }
        @Override
        public Object call() throws Exception {
            System.out.println("任务"+taskNum);
            return "MyCallable.call()-->task"+taskNum;
        }
    }
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        int num = 5;
        //创建一个线程池
        ExecutorService pool = Executors.newFixedThreadPool(num);
        List<Future> futureList = new ArrayList<Future>();
        for (int i = 0; i < num; i++){
            MyCallable mc = new MyCallable(i);
            //执行任务，并返回值
            Future future = pool.submit(mc);
            futureList.add(future);
        }
        pool.shutdown();
        for (Future f: futureList){
            System.out.println(f.get());
        }
    }
}

结果：