根据给定条件从 ArrayList 中删除对象 [英] Remove objects from an ArrayList based on a given criteria

问题描述

如果某个元素满足特定条件，我想从 Java 中的 ArrayList 中删除该元素.

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

即:

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

我能理解为什么这不起作用，但有什么好的方法可以做到这一点?

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

推荐答案

您必须使用 Iterator 进行迭代，并且迭代器的 remove 函数(不在列表中)) :

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，Iterator#remove 函数据说是可选，但它由 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.

这是来自 ArrayList.java 的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; 行就是为什么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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