根据给定条件从ArrayList中删除对象

问题描述

如果符合某个条件，我想从Java中的 ArrayList 中删除​​一个元素。

I would like to remove an element from an ArrayList in Java if it meets a certain criteria.

ie：

for (Pulse p : pulseArray) {
    if (p.getCurrent() == null) {
        pulseArray.remove(p);
    }
}

我能理解为什么这不起作用，但是什么这是一个很好的方法吗？

I can understand why this does not work, but what is a good way to do this?

推荐答案

你必须使用迭代器迭代和迭代器的删除函数（不是列表）：

You must use an Iterator to iterate and the remove function of the iterator (not of the list) :

Iterator<Pulse> iter = pulseArray.iterator();
while (iter.hasNext()) {
  Pulse p = iter.next();
  if (p.getCurrent()==null) iter.remove();
}

请注意函数被认为是optionnal但是由ArrayList的迭代器实现。

Note that the Iterator#remove function is said to be optionnal but it is implemented by the ArrayList's iterator.

这是ArrayList.java中这个具体函数的代码：

Here's the code of this concrete function from ArrayList.java :

765         public void remove() {
766             if (lastRet < 0)
767                 throw new IllegalStateException();
768             checkForComodification();
769
770             try {
771                 ArrayList.this.remove(lastRet);
772                 cursor = lastRet;
773                 lastRet = -1;
774                 expectedModCount = modCount;
775             } catch (IndexOutOfBoundsException ex) {
776                 throw new ConcurrentModificationException();
777             }
778         }
779
780         final void checkForComodification() {
781             if (modCount != expectedModCount)
782                 throw new ConcurrentModificationException();
783         }
784     }

expectedModCount = modCount; 行是在迭代时使用它时不会抛出异常的原因。

The expectedModCount = modCount; line is why it won't throw an exception when you use it while iterating.

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