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. }
    12. 将指定下标后面一位到数组末尾的全部元素向前移动一个单位，并且把数组最后一个元素设置为null，这样方便之后将整个数组不再使用时，
    13. 会被GC，可以作为小技巧。而需要移动的元素个数为：size-index-1
    1. public boolean remove(Object o) {  //只会删除集合中前面相同的元素
    2.     if (o == null) {
    3.         for (int index = 0; index < size; index++)
    4.             if (elementData[index] == null) {
    5.                 fastRemove(index);
    6.                 return true;
    7.             }
    8.     } else {
    9.         for (int index = 0; index < size; index++)
    10.             if (o.equals(elementData[index])) {
    11.                 fastRemove(index);
    12.                 return true;
    13.             }
    14.     }
    15.     return false;
    16. }
    1. private void fastRemove(int index) {
    2.     modCount++;
    3.     int numMoved = size - index - 1;
    4.     if (numMoved > 0)
    5.         System.arraycopy(elementData, index+1, elementData, index,
    6.                          numMoved);
    7.     elementData[--size] = null; // clear to let GC do its work
    8. }