Java并发学习之六——等待线程的终结

不念不忘少年蓝@ 2022-08-10 13:53 23阅读 0赞

本文是学习网络上的文章时的总结，感谢大家无私的分享。

1、在某些情况下，我们需要等待线程的终结。例如，我们可能会遇到程序在执行前需要初始化资源。在执行剩下的代码之前，我们需要等待线程完成初始化任务。为了达到此目的，我们使用Thread类的join()方法。当前线程调用某个线程的这个方法时，它会暂停当前线程，直到被调用线程执行完成。

2、Java提供2种形式的join（）方法：

Join(longmilliseconds)

Join(long milliseconds,long nanos)

第一种join方法，让调用线程等待特定的毫秒数。例如，如果thread1对象使用代码thread2.join(1000),那么线程thread1暂停运行，直到以下其中一个条件发生：

Thread2结束运行

1000毫秒过去了

当其中一个条件为真时，join()方法返回。

第二个版本的join方法和第一个很像，只不过它接收一个毫秒数和一个纳秒数作为参数。

举例

package chapter;
    
    import java.util.Date;
    import java.util.concurrent.TimeUnit;
    
    public class DataSourcesLoader implements Runnable{
    
    	@Override
    	public void run() {
    		System.out.printf("Beginning data sources loading : %s\n", new Date());
    		try {
    			TimeUnit.SECONDS.sleep(4);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		System.out.printf("Data sources loading has finished :%s\n",new Date());
    				
    	}
    }

package chapter;
    
    import java.util.Date;
    import java.util.concurrent.TimeUnit;
    
    public class NetwworkConnectionsLoader implements Runnable{
    
    	@Override
    	public void run() {
    		System.out.printf("Beginning Net sources loading : %s\n", new Date());
    		try {
    			TimeUnit.SECONDS.sleep(6);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		System.out.printf("Net sources loading has finished :%s\n",new Date());
    				
    	}
    }

package chapter;
    
    import java.util.Date;
    
    public class Main6 {
    
    	/**
    	 * <p>
    	 * </p>
    	 * @author zhangjunshuai
    	 * @date 2014-8-14 下午4:40:58
    	 * @param args
    	 * @throws InterruptedException 
    	 */
    	public static void main(String[] args) throws InterruptedException {
    
    		DataSourcesLoader dsLoader = new DataSourcesLoader();
    		Thread thread1 = new Thread(dsLoader,"DataSourcesLoader" +
    				"");
    		NetwworkConnectionsLoader ncLoader = new NetwworkConnectionsLoader();
    		Thread thread2 = new Thread(ncLoader,"NetwworkConnectionsLoader");
    		
    		thread1.start();
    		thread2.start();
    		
    		thread1.join();
    		thread2.join();
    		
    		System.out.printf("Main: Configuration has been loaded: %s\n",new Date());
    	}
    
    }

运行结果

![SouthEast][]

以上为书本示例，我在网上找了一个示例。

package mytest;
    class Thread1 extends Thread
    {
    	public Thread1(String threadName)
    	{	
    		super(threadName);
    	}
    	
    	public void run()
    	{
    		System.out.println(getName() + "is running");
    		try
    		{
    			sleep(2000);
    		} 
    		catch (InterruptedException e)
    		{
    			e.printStackTrace();
    		}
    		System.out.println("thread1 is over");	
    	}
    }

package mytest;
    class Thread2 extends Thread
    {
    	private Thread1 thread1;
    	
    	public Thread2(String threadName, Thread1 thread1)
    	{
    		super(threadName);
    		this.thread1 = thread1;		
    	}
    	
    	public void run()
    	{
    		System.out.println(getName() +  "is running");
    		try
    		{
    			thread1.start();
    			thread1.join();
    		} 
    		catch (InterruptedException e)
    		{
    			e.printStackTrace();
    		}
    		System.out.println("thread2 is over");	
    	}
    }

package mytest;
    public class JoinTest  
    {  
        public static void main(String[] args)  
        {  
            Thread1 thread1 = new Thread1("Thread1");  
            Thread2 thread2 = new Thread2("Thread2", thread1);  
            thread2.start();  
        }  
    }

运行结果  
![SouthEast 1][]

如果去除join方法

![SouthEast 2][]

[SouthEast]: /images/20220810/49609d5018f3494d81c9834ea8904548.png
[SouthEast 1]: /images/20220810/ff974fee59dc47ffb4bf111181aa97b1.png
[SouthEast 2]: /images/20220810/d2121a3374bd45cea7723778035de7c8.png