试图等待所有线程完成

Question

由于某些原因，在for循环中第二次迭代后，第二次启动thread1时，我得到一个java.lang.IllegalThreadStateException。我想我根据这里的答案How to wait for a number of threads to complete?正确使用加入。我的问题是为什么在第二次迭代时，我得到一个异常。

public void runThreads(){ 
     int numofTests; 
     Scanner in = new Scanner(System.in); 
     System.out.print("Enter the number of iterations to be completed:"); 
     numofTests = Integer.parseInt(in.nextLine());///Gets the number of tests from the user 
     Agent agent = new Agent(numofTests); 
     Smoker Pat = new Smoker ("paper", "Pam"); 
     Smoker Tom = new Smoker ("tobacco", "Tom"); 
     Smoker Matt = new Smoker ("matches", "Matt"); 
     Thread thread1 = new Thread(Pat); 
     Thread thread2 = new Thread(Tom); 
     Thread thread3 = new Thread(Matt); 
     Thread thread4 = new Thread(agent); 

     for (int i = 0; i < numofTests; i++){ 
     thread1.start(); 
     thread2.start(); 
     thread3.start(); 
     thread4.start(); 
     try { 
      thread1.join(); 
      thread2.join(); 
      thread3.join(); 
      thread4.join(); 
     } catch (InterruptedException e) { 
      Thread.currentThread().interrupt(); 
     } 
     } 

    } 

Answer 1

您无法多次启动线程。如果要多次执行可运行，请重新创建一个新线程。