thread.join函数，java多线程中的join函数解析

join函数的作用，是让当前线程等待，直到调用join（）的 线程结束或者等到一段时间，我们来看以下代码

 package mian;

 public class simpleplela {
     static void threadMessage(String message) {
         String threadName =
                 Thread.currentThread().getName();

           System.out.println(threadName+"   "+message
                    );
     }

     private static class MessageLoop
         implements Runnable {
         public void run(){

         String importantInfo[] = {
                 "ONe",
                 "TWo",
                 "THREe",
                 "four"
             };
         try{
             for(int i = 0;
                     i<importantInfo.length;
                     i++){
                 Thread.sleep(4000);
                 threadMessage(importantInfo[i]);
             }
         }
         catch(InterruptedException e){
             threadMessage("I was'nt done!");
         }
     }
     }
     public static void main(String args[])
         throws InterruptedException {
         long patience = 1000*10;
         if(args.length>0){
             try{
                 patience = Long.parseLong(args[0])*1000;
             }catch(NumberFormatException e){
                 System.err.println("Argument must be an integer");
                 System.exit(1);
             }
         }
         threadMessage("Starting MessageLoop Thread");
         long startTime = System.currentTimeMillis();
         Thread t = new Thread(new MessageLoop());
         t.start();
         threadMessage("Waiting for MEssageLoop Thread to finish");
         while((t.isAlive())){
             threadMessage("still waiting...");

             t.join();
             if (((System.currentTimeMillis() - startTime) > patience)
                     && t.isAlive()) {
                 threadMessage("Tired of waiting!");
                 t.interrupt();
                 // Shouldn't be long now
                 // -- wait indefinitely
                 t.join();
             }
             }
         threadMessage("Finally!");
     }

 }

输出如下

 package mian;

 public class simpleplela {
     static void threadMessage(String message) {
         String threadName =
                 Thread.currentThread().getName();

           System.out.println(threadName+"   "+message
                    );
     }

     private static class MessageLoop
         implements Runnable {
         public void run(){

         String importantInfo[] = {
                 "ONe",
                 "TWo",
                 "THREe",
                 "four"
             };
         try{
             for(int i = 0;
                     i<importantInfo.length;
                     i++){
                 Thread.sleep(4000);
                 threadMessage(importantInfo[i]);
             }
         }
         catch(InterruptedException e){
             threadMessage("I was'nt done!");
         }
     }
     }
     public static void main(String args[])
         throws InterruptedException {
         long patience = 1000*10;
         if(args.length>0){
             try{
                 patience = Long.parseLong(args[0])*1000;
             }catch(NumberFormatException e){
                 System.err.println("Argument must be an integer");
                 System.exit(1);
             }
         }
         threadMessage("Starting MessageLoop Thread");
         long startTime = System.currentTimeMillis();
         Thread t = new Thread(new MessageLoop());
         t.start();
         threadMessage("Waiting for MEssageLoop Thread to finish");
         while((t.isAlive())){
             threadMessage("still waiting...");

             t.join(1000);
             if (((System.currentTimeMillis() - startTime) > patience)
                     && t.isAlive()) {
                 threadMessage("Tired of waiting!");
                 t.interrupt();
                 // Shouldn't be long now
                 // -- wait indefinitely
                 t.join();
             }
             }
         threadMessage("Finally!");
     }

 }

输出如下 我们分析一下，两段代码只有一行不一样。第一段是t.join()，会让当前线程（例子中为主线程）一直等待，知道t结束；

第二段是t.join(1000),会让当前线程等待1000毫秒，之后继续。