java

     Waits for this thread to die.
    
     <p> An invocation of this method behaves in exactly the same
     way as the invocation
    
     <blockquote>
     {@linkplain #join(long) join}{@code (0)}
     </blockquote>
    
     @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 () throws InterruptedException {
       join(0);
   }

package com.king.learn;

public class MyJoin {
    public static void main(String[] args) throws InterruptedException {
        System.out.println("start");
        Thread t=new Thread(()->{
            for(int i=0;i<5;i++){
                System.out.println(i);
                try{
                    Thread.sleep(1000);
                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        });
        t.start();
        t.join();
        System.out.println("end");
    }
}

public final synchronized void (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;
        }
    }
}