实现多线程的四种方法

1.继承Thread类，重写run方法；
2.实现Runnable接口，重写run方法；
3.实现Callable接口，重写call方法；
4.通过线程池实现多线程（实现Runnable接口+Executors创建线程池）；

前2种方法无返回值，后2种方法有返回值。

继承Thread类，重写run方法

public class TTEST extends Thread{
 
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName());
    }
    
    public static void main(String[] args) {
        Thread t1 = new TTEST();
        Thread t2 = new TTEST();
        t1.setName("线程1");
        t2.setName("线程2");
        t1.start();
        t2.start();
    }

实现Runnable接口，重写run方法

public class RunnableThread implements Runnable{
 
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName());
    }
 
    public static void main(String[] args) {
        System.out.println(Thread.currentThread().getName());
        RunnableThread runnableThread = new RunnableThread();
        Thread t1 = new Thread(runnableThread);
        t1.setName("线程1");
        t1.start();
    }
    
}

实现Callable接口，重写call方法

因为FutureTask类实现了RunnaleFuture，而RunnaleFuture又实现了Runnable接口和Future接口，通过FutureTask封装继承Callable接口的类

import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
 
public class CollableThread implements Callable<Object>{
 
    @Override
    public Object call() throws Exception {
        System.out.println(Thread.currentThread().getName());
        return null;
    }
 
    public static void main(String[] args) {
        System.out.println(Thread.currentThread().getName());
        CollableThread collableThread = new CollableThread();
        FutureTask<Object> futureTask = new FutureTask<Object>(collableThread);
        Thread t1 = new Thread(futureTask);
        t1.setName("线程1");
        t1.start();
    }
    
}

通过线程池实现多线程（实现Runnable接口+Executors创建线程池）

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
 
public class PoolThread implements Runnable{
 
    private static int POOL_NUM = 10;//线程池数量
    
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName());
    }
 
    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newFixedThreadPool(5);
        for (int i = 0; i < POOL_NUM; i++) {
            PoolThread poolThread = new PoolThread();
            threadPool.execute(poolThread);
        }
        threadPool.shutdown();//关闭线程池
    }
    
}