/**
   * Waits for this thread to die.
   * 調(diào)用方線程（調(diào)用join方法的線程）執(zhí)行等待操作，直到被調(diào)用的線程（join方法所屬的線程）結(jié)束，再被喚醒
   * <p> An invocation of this method behaves in exactly the same
   * way as the invocation
   *
   *
   * @throws InterruptedException
   *     if any thread has interrupted the current thread. The
   *     <i>interrupted status</i> of the current thread is
   *     cleared when this exception is thrown.
   */
  public final void join() throws InterruptedException {
    join(0);
  }

/**
   * Waits at most {@code millis} milliseconds for this thread to
   * die. A timeout of {@code 0} means to wait forever.
   * 等待線程執(zhí)行結(jié)束，或者指定的最大等待時(shí)間到了，調(diào)用方線程再次被喚醒，如果最大等待時(shí)間為0，則只能等線程執(zhí)行結(jié)束，才能被喚醒。
   * <p> This implementation uses a loop of {@code this.wait} calls
   * conditioned on {@code this.isAlive}. As a thread terminates the
   * {@code this.notifyAll} method is invoked. It is recommended that
   * applications not use {@code wait}, {@code notify}, or
   * {@code notifyAll} on {@code Thread} instances.
   *
   * 
   */
  public final synchronized void join(long millis)
  throws InterruptedException {
    long base = System.currentTimeMillis();
    long now = 0;

    if (millis < 0) {
      throw new IllegalArgumentException("timeout value is negative");
    }

    if (millis == 0) {
      while (isAlive()) {
        wait(0);
      }
    } else {
      while (isAlive()) {
        long delay = millis - now;
        if (delay <= 0) {
          break;
        }
        wait(delay);
        now = System.currentTimeMillis() - base;
      }
    }
  }

//線程退出函數(shù)：
void JavaThread::exit(bool destroy_vm, ExitType exit_type) ｛
...
//這里會(huì)處理join相關(guān)的銷毀邏輯
ensure_join(this);
...
｝
//處理join相關(guān)的銷毀邏輯
  static void ensure_join(JavaThread* thread) {
   Handle threadObj(thread, thread->threadObj());

   ObjectLocker lock(threadObj, thread);

   thread->clear_pending_exception();

   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);

   java_lang_Thread::set_thread(threadObj(), NULL);

   //這里就調(diào)用notifyAll方法，喚醒等待的線程
   lock.notify_all(thread);

   thread->clear_pending_exception();
  }

public class JoinTest {
  
  public static void main(String[] args) {
    
    ThreadBoy boy = new ThreadBoy();
    boy.start();
    
  }
  
  static class ThreadBoy extends Thread{
    @Override
    public void run() {
      
      System.out.println("男孩和女孩準(zhǔn)備出去逛街");
      
      ThreadGirl girl = new ThreadGirl();
      girl.start();
      
      try {
        girl.join();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
      
      System.out.println("男孩和女孩開(kāi)始去逛街了");
    }
  }
  
  static class ThreadGirl extends Thread{
    @Override
    public void run() {
      int time = 5000;
      
      System.out.println("女孩開(kāi)始化妝,男孩在等待。。。");
      
      try {
        Thread.sleep(time);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
      
      System.out.println("女孩化妝完成！，耗時(shí)" + time);
      
    }
  }
  
}

public class JoinTest {
  
  public static void main(String[] args) {
    
    ThreadBoy boy = new ThreadBoy();
    boy.start();
    
  }
  
  static class ThreadBoy extends Thread{
    @Override
    public void run() {
      
      System.out.println("男孩和女孩準(zhǔn)備出去逛街");
      
      ThreadGirl girl = new ThreadGirl();
      girl.start();
      
      int time = 2000;
      try {
        girl.join(time);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
      
      System.out.println("男孩等了" + time + ", 不想再等了，去逛街了");
    }
  }
  
  static class ThreadGirl extends Thread{
    @Override
    public void run() {
      int time = 5000;
      
      System.out.println("女孩開(kāi)始化妝,男孩在等待。。。");
      
      try {
        Thread.sleep(time);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
      
      System.out.println("女孩化妝完成！，耗時(shí)" + time);
      
    }
  }
  
}