How to realize that all threads wait for an event to occur before executing

I wake up early and go to work every day, and my parents have to go to work every day. It is said that today I have booked a restaurant, and the family will have a meal together, and tell everyone to go to the restaurant to gather after get off work. Assumption: 3 people work in different places, and they have to wait for 3 people to arrive before they can eat. How to implement it with a program?

 

code show as below:

package com.qimh.concurrent;

import java.util.concurrent.CountDownLatch;

public class CountDownLatchDemo {
	
	
	
	
	 /** 
     * 模拟爸爸去饭店 
     */  
    public static void fatherToRes()  
    {  
        System.out.println("爸爸步行去饭店需要3小时。");  
    }  
  
    /** 
     * 模拟我去饭店 
     */  
    public static void motherToRes()  
    {  
        System.out.println("妈妈挤公交去饭店需要2小时。");  
    }  
  
    /** 
     * 模拟妈妈去饭店 
     */  
    public static void meToRes()  
    {  
        System.out.println("我乘地铁去饭店需要1小时。");  
    }  
  
    /** 
     * 模拟一家人到齐了 
     */  
    public static void togetherToEat()  
    {  
        System.out.println("一家人到齐了，开始吃饭");  
    }  

	
	private static CountDownLatch latch = new CountDownLatch(3);  
	  
    public static void main(String[] args) throws InterruptedException  
    {  
  
        new Thread()  
        {  
            public void run()  
            {  
                fatherToRes();  
                latch.countDown();  
            };  
        }.start();  
        new Thread()  
        {  
            public void run()  
            {  
                motherToRes();  
                latch.countDown();  
            };  
        }.start();  
        new Thread()  
        {  
            public void run()  
            {  
                meToRes();  
                latch.countDown();  
            };  
        }.start();  
  
        latch.await();  
        togetherToEat();  
    }  
}

Reference case: https://blog.csdn.net/lmj623565791/article/details/26626391