源码
// 根据位置移除元素，返回删除元素
public E remove(int index) {
rangeCheck(index);
modCount++;
E oldValue = elementData(index);
int numMoved = size – index – 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[–size] = null; // clear to let GC do its work
return oldValue;
}
// 根据元素移除元素
public boolean remove(Object o) {
if (o == null) {
for (int index = 0; index < size; index++)
if (elementData[index] == null) {
fastRemove(index);
return true;
}
} else {
for (int index = 0; index < size; index++)
if (o.equals(elementData[index])) {
fastRemove(index);
return true;
}
}
return false;
}
// 直接删除不返回删除的元素
private void fastRemove(int index) {
modCount++;
int numMoved = size – index – 1;
if (numMoved > 0)
System.arraycopy(elementData, index+1, elementData, index,
numMoved);
elementData[–size] = null; // clear to let GC do its work
}
// 移除指定范围的元素
protected void removeRange(int fromIndex, int toIndex) {
modCount++;
int numMoved = size – toIndex;
System.arraycopy(elementData, toIndex, elementData, fromIndex,
numMoved);
// clear to let GC do its work
int newSize = size – (toIndex-fromIndex);
for (int i = newSize; i < size; i++) {
elementData[i] = null;
}
size = newSize;
}
// 移除所有在传入参入集合内的参数
public boolean removeAll(Collection<?> c) {
Objects.requireNonNull(c);
return batchRemove(c, false);
}
// 清空队列内元素，但队列还实际存在
public void clear() {
modCount++;
// clear to let GC do its work
for (int i = 0; i < size; i++)
elementData[i] = null;
size = 0;
}