当引发异常时，EDT是否重新启动？

Question

（下面的示例代码是自包含的，可运行的，你可以尝试，它不会造成系统崩溃:)

汤姆Hawtin评论的问题在这里：Why do people run Java GUI's on the Event Queue

说：

EDT不太可能会崩溃。在EDT调度中抛出的未经检查的异常被捕获，抛弃并且线程继续。

有人可以解释我是怎么回事就在这里（你点击每次“抛出一个未经检查的异常”按钮，执行零一分，故意）：

import javax.swing.*; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.WindowAdapter; 
import java.awt.event.WindowEvent; 

public class CrashEDT extends JFrame { 

    public static void main(String[] args) { 
     final CrashEDT frame = new CrashEDT(); 
     frame.addWindowListener(new WindowAdapter() { 
      public void windowClosing(WindowEvent e) { 
       System.exit(0); 
      } 
     }); 
     final JButton jb = new JButton("throw an unchecked exception"); 
     jb.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
       System.out.println("Thread ID:" + Thread.currentThread().getId()); 
       System.out.println(0/Math.abs(0)); 
      } 
     }); 
     frame.add(jb); 
     frame.setSize(300, 150); 
     frame.setVisible(true); 
    } 

} 

我得到以下消息（这是我所期望的）：

Exception in thread "AWT-EventQueue-0" java.lang.ArithmeticException:/by zero 

对我来说这是一个未经检查的异常吗？

您可以看到每次触发崩溃时线程ID都会增加。

因此，EDT每次都会自动重新启动一个未经检查的异常或未经检查的异常“被捕获，倾销和线程继续”像Tom Hawtin所评论的那样？

这是怎么回事？

Answer 1

供参考“的this machinery的特定行为是依赖于实现“。例如，线程ID在我的平台上保持不变。在AWT Threading Issues中讨论的净效果是“当有至少一个可显示组件时，JVM不会退出”。

Answer 2

有趣的问题。我会认为，例外被捕获，线程继续，但经过一些研究，我不太确定。

我有

Set<Thread> seenAwtThreads = new HashSet<Thread>(); 

中，我收集了所有“看见” AWT线程扩展程序，以及集的大小，每次我点击“抛出异常”按钮上，这似乎增加建议在发生异常时初始化新线程。

最后我发现，在run实施EventDispatchThread此评论：

/* 
* Event dispatch thread dies in case of an uncaught exception. 
* A new event dispatch thread for this queue will be started 
* only if a new event is posted to it. In case if no more 
* events are posted after this thread died all events that 
* currently are in the queue will never be dispatched. 
*/ 

完整运行方法的实现是这样的：

public void run() { 
    try { 
     pumpEvents(new Conditional() { 
      public boolean evaluate() { 
       return true; 
      } 
     });  
    } finally { 
     /* 
     * This synchronized block is to secure that the event dispatch 
     * thread won't die in the middle of posting a new event to the 
     * associated event queue. It is important because we notify 
     * that the event dispatch thread is busy after posting a new event 
     * to its queue, so the EventQueue.dispatchThread reference must 
     * be valid at that point. 
     */ 
     synchronized (theQueue) { 
      if (theQueue.getDispatchThread() == this) { 
       theQueue.detachDispatchThread(); 
      } 
      /* 
      * Event dispatch thread dies in case of an uncaught exception. 
      * A new event dispatch thread for this queue will be started 
      * only if a new event is posted to it. In case if no more 
      * events are posted after this thread died all events that 
      * currently are in the queue will never be dispatched. 
      */ 
      /* 
      * Fix for 4648733. Check both the associated java event 
      * queue and the PostEventQueue. 
      */ 
      if (theQueue.peekEvent() != null || 
       !SunToolkit.isPostEventQueueEmpty()) { 
       theQueue.initDispatchThread(); 
      } 
      AWTAutoShutdown.getInstance().notifyThreadFree(this); 
     } 
    } 
} 

Answer 3

在事件派发线程上设置了一个默认的UncaughtExceptionHandler，它将System.out的Exception打印出来，然后在Thread中继续。