Thread之join()解析

调用thread.join()方法的线程，需要等待thread完成后才能继续执行代码。
例子：线程main和Thread-0～1依次等待前一个线程完成后，才能继续执行join()方法之后的代码。

package com.join;

import java.util.concurrent.TimeUnit;

public class Join {
    public static void main(String[] args) throws InterruptedException {
        Thread previous = Thread.currentThread();
        for (int i = 0; i < 10; i++) {
            Thread thread = new Thread(new Recurse(previous), "Thread-" + i);
            thread.start();
            previous = thread;
        }
        TimeUnit.SECONDS.sleep(4);
        System.out.println("Thread-" + Thread.currentThread().getName() + " is terminated.");
    }

    static class Recurse implements Runnable {
        private Thread thread;
        public Recurse(Thread thread) {
            this.thread = thread;
        }

        @Override
        public void run() {
            try {
                thread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + " is terminated.");
        }
    }
}