首先说下不正确的打开方式：
第一：使用for循环删除集合的元素，示例代码如下
1 ArrayList<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c", "d"));
2 for (int i = 0; i < list.size(); i++) {
3 list.remove(i);
4 }
5 System.out.println(list);
结果输出为：
[b, d]
解说开始：
首先看下源码：
1 public E remove(int index) {
2 rangeCheck(index);
3 modCount++;
4 E oldValue = elementData(index);
5 int numMoved = size - index - 1;
6 if (numMoved > 0)
7 System.arraycopy(elementData, index+1, elementData, index,
8 numMoved);
9 elementData[--size] = null; // clear to let GC do its work
10 return oldValue;
11 }
解释：第一次进for循环，i=0 ，调用remove方法删除第一位的元素， 集合大小收缩，第一次删除完成后，list变成【b,c,d】；再次循环，i=1，调用remove方法删除了c 集合大小再次收缩，list变成【b,d】；再次循环，i=2，不符合条件，循环结束
第二：使用foreach循环删除元素，示例代码如下
1 ArrayList<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c", "d"));
2 for (String s : list) {
3 if (s.equals("b"))
4 list.remove(s);
5 }
6 System.out.println(list);
结果：这段代码居然抛出了异常 java.util.ConcurrentModificationException。
解说开始：
首先看下源代码：
1 public Iterator<E> iterator() {
2 return new Itr();
3 }
4 /**
5 * An optimized version of AbstractList.Itr
6 */
7 private class Itr implements Iterator<E> {
8 int cursor; // index of next element to return
9 int lastRet = -1; // index of last element returned; -1 if no such
10 int expectedModCount = modCount;
11 public boolean hasNext() {
12 return cursor != size;
13 }
14 @SuppressWarnings("unchecked")
15 public E next() {
16 checkForComodification();
17 int i = cursor;
18 if (i >= size)
19 throw new NoSuchElementException();
20 Object[] elementData = ArrayList.this.elementData;
21 if (i >= elementData.length)
22 throw new ConcurrentModificationException();
23 cursor = i + 1;
24 return (E) elementData[lastRet = i];
25 }
26 public void remove() {
27 if (lastRet < 0)
28 throw new IllegalStateException();
29 checkForComodification();
30 try {
31 ArrayList.this.remove(lastRet);
32 cursor = lastRet;
33 lastRet = -1;
34 expectedModCount = modCount;
35 } catch (IndexOutOfBoundsException ex) {
36 throw new ConcurrentModificationException();
37 }
38 }
39 final void checkForComodification() {
40 if (modCount != expectedModCount)
41 throw new ConcurrentModificationException();
42 }
43 }
解释：在Java中的foreach循环的工作原理就像一个iterator。
so，接下来说下正确的打开方式——
1 ArrayList<Integer> a=new ArrayList<Integer>(15);
2 a.add(222);
3 a.add(3);
4 a.add(333);
5 a.add(000);
6 a.add(333);
7 a.add(4);
8
9 for(int s=a.size()-1;s>=0;s--){
10 if(a.get(s).intValue()==333){
11 a.remove(s);
12 }
13 }
1 privatevoid screenBlackNameList(List<SharedBoardSmsWrapper> source, List<BlackNameListModel> blackNameList){
2 Iterator<SharedBoardSmsWrapper> sourceIt=source.iterator();
3 while(sourceIt.hasNext()){
4 SharedBoardSmsWrapper tmpSharedBoardSmsWrapper=sourceIt.next();
5 Iterator<BlackNameListModel> blackNameListIt=blackNameList.iterator();
6 while(blackNameListIt.hasNext()){
7 BlackNameListModel tmpBlackNameListModel=blackNameListIt.next();
8 if(tmpSharedBoardSmsWrapper.getSource().equals(tmpBlackNameListModel.getSource())){
9 sourceIt.remove();
10 break;
11 }
12 }
13 }
14 }
原文：http://www.cnblogs.com/mayiwen/p/5530856.html