实现方式多种多样，下面列两种供参考：

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.*;public class Main {

public static void main(String[] args) throws InterruptedException, ExecutionException {

System.out.println("方式1");

System.out.println("================================================");

// 方式1

// 创建一个线程池，并创建10个线程放入线程池执行

ExecutorService pool = Executors.newCachedThreadPool();

for (int i = 0; i < 10; i++) {

pool.execute(new MyThread("线程" + i));

}

// 线程池不再接收新任务

pool.shutdown();

// 线程池中的所有线程都执行完pool.isTerminated()才返回true

while (!pool.isTerminated()) {

Thread.sleep(100);

}

System.out.println("所有线程执行完成");

System.out.println("

方式2");

System.out.println("================================================");

// 方式2

ExecutorService pool2 = Executors.newCachedThreadPool();

List futures = new ArrayList<>();

for (int i = 0; i < 10; i++) {

// 使用实现Callable接口的方式创建线程，通过Future可以获取线程中返回的结果

Future future = pool2.submit(new MyThread2("线程" + i));

futures.add(future);

}

for (Future future : futures) {

// 该方法会阻塞主线程，直到线程执行完成

future.get();

}

System.out.println("所有线程执行完成");

}

}

class MyThread extends Thread {

private String name;

public MyThread(String name) {

this.name = name;

}

@Override

public void run() {

try {

Thread.sleep(3000);

} catch (InterruptedException e) {

e.printStackTrace();

}

System.out.println(name + "执行完成");

}

}class MyThread2 implements Callable {

private String name;

public MyThread2(String name) {

this.name = name;

}

@Override

public Object call() throws Exception {

try {

Thread.sleep(3000);

} catch (InterruptedException e) {

e.printStackTrace();

}

System.out.println(name + "执行完成");

return null;

}

}