器：JVM永遠不會停止

public static void main(String[] args) throws Exception { 
    final Exchanger<String> exchanger = new Exchanger<String>(); 
    new Thread(new Runnable() { 
     @Override 
     public void run() { 
      try { 
       System.out.println(Thread.currentThread().getName() + exchanger.exchange("this came from subthread")); 
      } catch (InterruptedException ex) { 
       System.out.println("interrupted while waiting for message"); 
      } 
     } 
    }).start(); 

    System.out.println(Thread.currentThread().getName() + exchanger.exchange("this came from main thread")); 
    String s = exchanger.exchange("this came from main thread"); 
}

輸出器：JVM永遠不會停止

mainthis came from subthread 
Thread-0this came from main thread

爲什麼在JVM永不放棄嗎？

來源

2012-12-21 Achow

在您的主題中有一個交換點，但在主線程中有兩個交換點。所以第二個交換：String s = exchanger.exchange("this came from main thread");永遠等待並阻止JVM退出。如果在該行之後添加打印語句，您將看到它不會被執行。

如果添加在你的線程第二交換，該程序將退出：

public void run() { 
    try { 
     System.out.println(Thread.currentThread().getName() + exchanger.exchange("this came from subthread")); 
     exchanger.exchange("allow JVM to exit here"); 
    } catch (InterruptedException ex) { 
     System.out.println("interrupted while waiting for message"); 
    } 
}

來源

2012-12-21 09:58:33 assylias

如果主方法中的最後一行被刪除，該怎麼辦？ – Subin

@SubinS也可以。 – assylias

當然，這是從我這樣一個愚蠢的問題..有一次，複製粘貼導致了這個錯誤...應該已經看到我的代碼在這裏..在日食，不知何故這兩行是並排粘貼，所以我完全錯過了.. :( – Achow

最後一行：

String s = exchanger.exchange("this came from main thread");

提供"this came from main thread"與一些其他線程交換，但沒有其他線索來提出還價。

來源

2012-12-21 10:01:20

器：JVM永遠不會停止

回答

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