回到命令行程序時輸出完成

Question

寫了多線程程序的順序打印出單雙號直到序列達到30

import java.util.concurrent.Executor; 
import java.util.concurrent.Executors; 
import java.util.concurrent.atomic.AtomicInteger; 

public class NumPrintTX 
{ 
public static void main(String[] args) 
{ 
    final int max = 31; 
    final AtomicInteger i = new AtomicInteger(0); 
    Executor dd = Executors.newFixedThreadPool(2); 

    final Object lock = new Object(); 

    dd.execute(new Runnable() 
    { 
     @Override 
     public void run() 
     { 
      while (i.get() < max) 
      { 
       if (i.get() % 2 == 0) 
       { 
        System.out.print(" " + i.getAndAdd(1)); 

        synchronized(lock) 
        { 
         lock.notify(); 
        } 
       } 
       else 
       { 
        synchronized(lock) 
        { 
         try 
         { 
          lock.wait(); 
         } 
         catch (InterruptedException e) 
         { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
        } 
       } 
      } 
     } 
    }); 
    dd.execute(new Runnable() 
    { 
     @Override 
     public void run() 
     { 
      while (i.get() < max) 
      { 
       if (i.get() % 2 != 0) 
       { 
        System.out.print(" " + i.getAndAdd(1)); 

        synchronized(lock) 
        { 
         lock.notify(); 
        } 
       } 
       else 
       { 
        synchronized(lock) 
        { 
         try 
         { 
          lock.wait(); 
         } 
         catch (InterruptedException e) 
         { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
        } 
       } 
      } 
     } 
    }); 
    do 
    { 
     try 
     { 
      Thread.currentThread().sleep(1000); 
      } 
     catch (InterruptedException e) 
     { 
      e.printStackTrace(); 
     } 
    } 
    while (i.get() != max); 
} 
} 

程序運行時

，它出來就好了，但它不會進入下一行，所以我可以輸入另一個命令，用於接下來要做的任何事情。任何想法，爲什麼這是我能做些什麼來解決它？

修改後的代碼： import java.util.concurrent.Executor; import java.util.concurrent.Executors; import java.util.concurrent.atomic.AtomicInteger;

public class NumPrintTX 
{ 
public static void main(String[] args) 
{ 
    final int max = 31; 
    final AtomicInteger i = new AtomicInteger(0); 
    Executor dd = Executors.newFixedThreadPool(2); 

    final Object lock = new Object(); 

    dd.execute(new Runnable() 
    { 
     @Override 
     public void run() 
     { 
      while (i.get() < max) 
      { 
       if (i.get() % 2 == 0) 
       { 
        System.out.print(" " + i.getAndAdd(1)); 

        synchronized(lock) 
        { 
         lock.notify(); 
        } 
       } 
       else 
       { 
        synchronized(lock) 
        { 
         try 
         { 
          lock.wait(); 
         } 
         catch (InterruptedException e) 
         { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
        } 
       } 
      } 
     } 
    }); 
    dd.execute(new Runnable() 
    { 
     @Override 
     public void run() 
     { 
      while (i.get() < max) 
      { 
       if (i.get() % 2 != 0) 
       { 
        System.out.print(" " + i.getAndAdd(1)); 

        synchronized(lock) 
        { 
         lock.notify(); 
        } 
       } 
       else 
       { 
        synchronized(lock) 
        { 
         try 
         { 
          lock.wait(); 
         } 
         catch (InterruptedException e) 
         { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
         } 
        } 
       } 
      } 
     } 
    }); 
    do 
    { 
     try 
     { 
      Thread.currentThread().sleep(1000); 
      } 
     catch (InterruptedException e) 
     { 
      e.printStackTrace(); 
     } 
    } 
    while (i.get() != max); 
} 
public void close() 
{ 
System.exit(0); 
} 
} 

Answer 1

你不能阻止你的線程池，所以它不是讓你的主程序結束。

考慮下面的代碼：

import java.util.concurrent.Executors; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.atomic.AtomicInteger; 

class Worker implements Runnable { 
    private AtomicInteger i; 
    private Object lock; 
    private int max; 
    private int mod; 

    Worker(AtomicInteger i_, Object lock_, int max_, int mod_){ 
     this.i = i_; 
     this.lock = lock_; 
     this.max = max_; 
     this.mod = mod_; 
    } 

    @Override 
    public void run(){ 
     while (i.get() < max) 
     { 
      if(i.get() % 2 == mod) 
      { 
       System.out.print(" " + i.getAndAdd(1)); 

       synchronized(lock){ lock.notify(); } 
      } 
      else 
      { 
       synchronized(lock) 
       { 
        try { lock.wait(); } 
        catch (InterruptedException e) { e.printStackTrace(); } 
       } 
      } 
     } 
    } 
} 

public class NumPrintTX 
{ 
    public static void main(String[] args) 
    { 
     final int max = 31; 
     final AtomicInteger i = new AtomicInteger(0); 
     ExecutorService dd = Executors.newFixedThreadPool(2); 

     final Object lock = new Object(); 

     dd.execute(new Worker(i, lock, max, 0)); 
     dd.execute(new Worker(i, lock, max, 1)); 

     dd.shutdown(); 
    }  
} 

沒有dd.shutdown()，你的程序將被掛起，儘管越來越到底。

主do-while循環和System.exit(0)會工作，但似乎有點「蠻力」。

此外，此代碼簡化了您的線程代碼，使其更易讀，而無需更改基礎邏輯。

Answer 2

您需要與System.exit(0);調用其中0是一個「正常的」退出的退出狀態碼退出程序。呼叫應該在您的循環打印出數字已完成後進行。

Java Docs for System.exit(int status)

Answer 3

您需要明確關閉程序。所以，這樣的事情：

public void close() { 
    // Put any closing code here, like joining Threads or whatever 
    System.exit(0); // 0 means it is a normal exit, i.e. there are no errors 
}