Java-同步列表

Question

我已经在这个问题上停留了一段时间，所以非常感谢任何帮助。

我有以下代码部分:

BallThread.java
@Override
public synchronized void run() {
  while (numItersCompleted < maxNumIters) {
    completedThisIter = false;
synchronized (ballList) {
    for (Ball b : ballList) { // line 35
        b.updatePosition(ballPanel.getBounds(), ballList);
    }
}
 } // other stuff


Exception in thread "Thread-2" java.util.ConcurrentModificationException
at java.util.ArrayList$SubList.checkForComodification(ArrayList.java:1091)
at java.util.ArrayList$SubList.listIterator(ArrayList.java:972)
at java.util.AbstractList.listIterator(AbstractList.java:300)
at java.util.ArrayList$SubList.iterator(ArrayList.java:968)
at Part2.BallThread.run(BallThread.java:35)

有时我会得到这个(BallPanel 中的第 36 行)

java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:782)
at java.util.ArrayList$Itr.next(ArrayList.java:754)
at Part2.BallPanel.paintComponent(BallPanel.java:36)
at javax.swing.JComponent.paint(JComponent.java:1029)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5138)
at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:302)
at javax.swing.RepaintManager.paint(RepaintManager.java:1188)
at javax.swing.JComponent._paintImmediately(JComponent.java:5086)
at javax.swing.JComponent.paintImmediately(JComponent.java:4896)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:783)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:735)

Answer 1

在看不到其余代码的情况下，一种解决方法是将 ballList 声明如下:

private final List<Ball> ballList = Collections.synchronizedList(...);

synchronizedList 的所有操作尝试在每个方法之前同步自身，这将使您的迭代完全安全，只要您保持当前的 synchronized(ballList) 就位。