Java object wait notify notifyAll代码解析

public static Object loc=new Object();

  public static void main(String[] args) throws Exception{

    Thread t1=new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          java.text.SimpleDateFormat sdf=new SimpleDateFormat("HH:mm:ss SSS");
          System.out.println("["+sdf.format(new Date())+"] t1___等待锁...");
          synchronized (loc) {
            System.out.println("["+sdf.format(new Date())+"] t1___获得锁 ...");
            Thread.sleep(5000);
            System.out.println("["+sdf.format(new Date())+"] t1___loc..开始执行wait...");
            loc.wait();
            System.out.println("["+sdf.format(new Date())+"] t1___loc..执行wait后续...");
            Thread.sleep(1000);
          }
          System.out.println("["+sdf.format(new Date())+"] t1___loc..离开锁...");
        }catch (Exception e){
          e.printStackTrace();
        }
      }
    });
    Thread t3=new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          java.text.SimpleDateFormat sdf=new SimpleDateFormat("HH:mm:ss SSS");
          System.out.println("["+sdf.format(new Date())+"] t3___等待锁...");
          synchronized (loc) {
            System.out.println("["+sdf.format(new Date())+"] t3___进入锁...");
            Thread.sleep(5000);
            System.out.println("["+sdf.format(new Date())+"] t3___loc..开始 wait...");
            loc.wait();
            System.out.println("["+sdf.format(new Date())+"] t3___loc..执行 wait后续...");
            Thread.sleep(1000);
          }
          System.out.println("["+sdf.format(new Date())+"] t3___离开锁...");
        }catch (Exception e){
          e.printStackTrace();
        }
      }
    });

    Thread t2=new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          java.text.SimpleDateFormat sdf=new SimpleDateFormat("HH:mm:ss SSS");
          System.out.println("["+sdf.format(new Date())+"] t2___等待锁...");
          synchronized (loc) {
            System.out.println("["+sdf.format(new Date())+"] t2___获得锁...");
            Thread.sleep(5000);
            System.out.println("["+sdf.format(new Date())+"] t2___loc..开始执行 notify...");
            loc.notify();
            System.out.println("["+sdf.format(new Date())+"] t2___loc..执行 notify后续...");
            Thread.sleep(1000);
          }
          System.out.println("["+sdf.format(new Date())+"] t2___loc 离开锁....");
        }catch (Exception e){
          e.printStackTrace();
        }
      }
    });
    t1.start();
    t3.start();
    Thread.sleep(500);
    t2.start();


    System.out.println("t1___before join ....");
    t1.join();
    System.out.println("t2___before join ....");
    t2.join();
    System.out.println("t3____before join ....");
    t3.join();
    System.out.println("main exit....");
  }