如何处理ConcurrentModificationException [英] How to deal with ConcurrentModificationException

问题描述

我从我的冷却计时器中得到一个ConcurrentModificationException。我使用一个线程来减少每秒这样的值：

  public class CoolDownTimer implements Runnable {
 @Override 
 public void run（）{
 for（String s：playerCooldowns.keySet（））{
 playerCooldowns.put（s，playerCooldowns.get（s） -  20）; 
 if（playerCooldowns.get（s）<= 0）{
 playerCooldowns.remove（s）; 
 
 
 
 
 
 
 
 
 
所以每秒钟都应该把每个玩家的冷却时间减少20个，但问题是我每隔几个小时就会得到一个CME，特别是在很多人在线的时候。我如何做到这一点，如果它仍然在修改列表，它会等到当前的操作完成并创建一个修改队列的种类？谢谢！这里是堆栈跟踪：
 
 
  2012-06-18 20:59:05 [警告]任务'SurvivorsClasses'生成一个例外
 java.util.ConcurrentModificationException $ b $在java.util.HashMap $ HashIterator.nextEntry（HashMap.java:839）$ b $在java.util.HashMap $ KeyIterator.next（HashMap.java： 874）
 at me.zachoooo.survivorclasses.CoolDownManager $ CoolDownTimer.run（CoolDownManager.java:13）
 at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat（CraftScheduler.java:126）
 at net.minecraft.server.MinecraftServer.w（MinecraftServer.java:533）
 at net.minecraft.server.MinecraftServer.run（MinecraftServer.java:459）
  
解决方案
  / div> 
使用foreach循环时不能修改集合。 
 
 $ b 您可以遍历 Map.entrySet（）需要： 
 
 
  public void run（）{
 for（Iterator< Map.Entry< String，Integer>> i = playerCooldowns.entrySet（）。iterator（）; i.hasNext（）;）{
 Map.Entry< String，Integer> entry = i.next（）; 
 entry.setValue（entry.getValue（） -  20）; //通过Map.Entry更新
 if（entry.getValue（）< = 0）{
 i.remove（）; //通过迭代器移除
 
 
 
 code $ pre 
I am getting the a ConcurrentModificationException from my cooldown timer. I use a thread to reduce the values every second like this:
public class CoolDownTimer implements Runnable {
    @Override
    public void run() {
        for (String s : playerCooldowns.keySet()) {
            playerCooldowns.put(s, playerCooldowns.get(s) - 20);
            if (playerCooldowns.get(s) <= 0) {
                playerCooldowns.remove(s);
            }
        }
    }

}
So every second it should reduce every players cooldown by 20, but the problem is that I a getting the CME every couple hours while running the program, especially when lots of people are online. How do I make it so that if it is still modifying the list, it will wait until the current operation is done and create a sort of modification queue? Thanks! Here is the stack trace:
2012-06-18 20:59:05 [WARNING] Task of 'SurvivorsClasses' generated an exception
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:839)
at java.util.HashMap$KeyIterator.next(HashMap.java:874)
at me.zachoooo.survivorclasses.CoolDownManager$CoolDownTimer.run(CoolDownManager.java:13)
at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:126)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:533)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:459)
Line 13 is the start of the for loop...
解决方案
You can't modify collections when using a foreach loop. 

You can however iterate over the Map.entrySet() and do everything you need:
public void run() {
    for (Iterator<Map.Entry<String,Integer>> i = playerCooldowns.entrySet().iterator(); i.hasNext();) {
        Map.Entry<String,Integer> entry = i.next();
        entry.setValue(entry.getValue() - 20); // update via the Map.Entry
        if (entry.getValue() <= 0) {
            i.remove(); // remove via the iterator
        }
    }
}


                        
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