如何调试ConcurrentModificationException？ [英] How to debug ConcurrentModificationException?

问题描述

我遇到ConcurrentModificationException，通过查看它，我看不到它发生的原因;抛出异常的区域和修改集合的所有位置都被

I encountered ConcurrentModificationException and by looking at it I can't see the reason why it's happening; the area throwing the exception and all the places modifying the collection are surrounded by

synchronized (this.locks.get(id)) {
  ...
} // locks is a HashMap<String, Object>;

我试图抓住那个讨厌的线程，但我只能钉住（通过在异常中设置一个断点）是抛出线程拥有监视器，而另一个线程（程序中有两个线程）会休眠。

I tried to catch the the pesky thread but all I could nail (by setting a breakpoint in the exception) is that the throwing thread owns the monitor while the other thread (there are two threads in the program) sleeps.

我应该如何进行？当遇到类似的线程问题时，通常做什么？

How should I proceed? What do you usually do when you encounter similar threading issues?

推荐答案

它可能与同步块无关。 ConcurrentModificationException 经常发生在您在迭代其元素时修改集合。

It may have nothing to do with the synchronization block. ConcurrentModificationExceptions often occur when you're modifying a collection while you are iterating over its elements.

List<String> messages = ...;
for (String message : messages) {
    // Prone to ConcurrentModificationException
    messages.add("A COMPLETELY NEW MESSAGE");
}

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