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

 1 package mian;
 2
 3
 4 public class simpleplela {
 5     static void threadMessage(String message) {
 6         String threadName =
 7                 Thread.currentThread().getName();
 8
 9           System.out.println(threadName+"   "+message
10                    );
11     }
12
13     private static class MessageLoop
14         implements Runnable {
15         public void run(){
16
17
18         String importantInfo[] = {
19                 "ONe",
20                 "TWo",
21                 "THREe",
22                 "four"
23             };
24         try{
25             for(int i = 0;
26                     i<importantInfo.length;
27                     i++){
28                 Thread.sleep(4000);
29                 threadMessage(importantInfo[i]);
30             }
31         }
32         catch(InterruptedException e){
33             threadMessage("I was‘nt done!");
34         }
35     }
36     }
37     public static void main(String args[])
38         throws InterruptedException {
39         long patience = 1000*10;
40         if(args.length>0){
41             try{
42                 patience = Long.parseLong(args[0])*1000;
43             }catch(NumberFormatException e){
44                 System.err.println("Argument must be an integer");
45                 System.exit(1);
46             }
47         }
48         threadMessage("Starting MessageLoop Thread");
49         long startTime = System.currentTimeMillis();
50         Thread t = new Thread(new MessageLoop());
51         t.start();
52         threadMessage("Waiting for MEssageLoop Thread to finish");
53         while((t.isAlive())){
54             threadMessage("still waiting...");
55
56             t.join();
57             if (((System.currentTimeMillis() - startTime) > patience)
58                     && t.isAlive()) {
59                 threadMessage("Tired of waiting!");
60                 t.interrupt();
61                 // Shouldn‘t be long now
62                 // -- wait indefinitely
63                 t.join();
64             }
65             }
66         threadMessage("Finally!");
67     }
68
69 }

输出如下

 1 package mian;
 2
 3
 4 public class simpleplela {
 5     static void threadMessage(String message) {
 6         String threadName =
 7                 Thread.currentThread().getName();
 8
 9           System.out.println(threadName+"   "+message
10                    );
11     }
12
13     private static class MessageLoop
14         implements Runnable {
15         public void run(){
16
17
18         String importantInfo[] = {
19                 "ONe",
20                 "TWo",
21                 "THREe",
22                 "four"
23             };
24         try{
25             for(int i = 0;
26                     i<importantInfo.length;
27                     i++){
28                 Thread.sleep(4000);
29                 threadMessage(importantInfo[i]);
30             }
31         }
32         catch(InterruptedException e){
33             threadMessage("I was‘nt done!");
34         }
35     }
36     }
37     public static void main(String args[])
38         throws InterruptedException {
39         long patience = 1000*10;
40         if(args.length>0){
41             try{
42                 patience = Long.parseLong(args[0])*1000;
43             }catch(NumberFormatException e){
44                 System.err.println("Argument must be an integer");
45                 System.exit(1);
46             }
47         }
48         threadMessage("Starting MessageLoop Thread");
49         long startTime = System.currentTimeMillis();
50         Thread t = new Thread(new MessageLoop());
51         t.start();
52         threadMessage("Waiting for MEssageLoop Thread to finish");
53         while((t.isAlive())){
54             threadMessage("still waiting...");
55
56             t.join(1000);
57             if (((System.currentTimeMillis() - startTime) > patience)
58                     && t.isAlive()) {
59                 threadMessage("Tired of waiting!");
60                 t.interrupt();
61                 // Shouldn‘t be long now
62                 // -- wait indefinitely
63                 t.join();
64             }
65             }
66         threadMessage("Finally!");
67     }
68
69 }

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。

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