JDK7中的LinkedList中的addAll会先将要添加的Collection做toArray转化,然后在去迭代toArray后的数组进行添加操作,为什么不直接迭代Collection呢?难道只为了多线程下直接迭代Collection会有异常而进行这样的转化吗?
JDK7的代码如下:
[code="java"]
public boolean addAll(int index, Collection<? extends E> c) {
checkPositionIndex(index);
Object[] a = c.toArray();
int numNew = a.length;
if (numNew == 0)
return false;
Node<E> pred, succ;
if (index == size) {
succ = null;
pred = last;
} else {
succ = node(index);
pred = succ.prev;
}
for (Object o : a) {
@SuppressWarnings("unchecked") E e = (E) o;
Node<E> newNode = new Node<>(pred, e, null);
if (pred == null)
first = newNode;
else
pred.next = newNode;
pred = newNode;
}
if (succ == null) {
last = pred;
} else {
pred.next = succ;
succ.prev = pred;
}
size += numNew;
modCount++;
return true;
}
[/code]