早上看linkedList源码时候，对于它的初始化一直不太明白。如下:
transient int size = 0;
/**
* Pointer to first node.
* Invariant: (first == null && last == null) ||
* (first.prev == null && first.item != null)
*/
transient Node<E> first;
/**
* Pointer to last node.
* Invariant: (first == null && last == null) ||
* (last.next == null && last.item != null)
*/
transient Node<E> last;
/**
* Inserts all of the elements in the specified collection into this
* list, starting at the specified position. Shifts the element
* currently at that position (if any) and any subsequent elements to
* the right (increases their indices). The new elements will appear
* in the list in the order that they are returned by the
* specified collection's iterator.
*
* @param index index at which to insert the first element
* from the specified collection
* @param c collection containing elements to be added to this list
* @return {@code true} if this list changed as a result of the call
* @throws IndexOutOfBoundsException {@inheritDoc}
* @throws NullPointerException if the specified collection is null
*/
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;
}
一直不明白怎么赋值的。跟着代码调试后，刚开始是null，使用的时候每次add,然后再去赋值。大概过程如下：
另一个构造方法是带Collection值得对象作为入参的构造函数的，下面是执行逻辑：
1）使用this（）调用默认的无参构造函数。
2）调用addAll（）方法，传入当前的节点个数size，此时size为0，并将collection对象传递进去
3）检查index有没有数组越界的嫌疑
4）将collection转换成数组对象a
5）循环遍历a数组，然后将a数组里面的元素创建成拥有前后连接的节点，然后一个个按照顺序连起来。
6）修改当前的节点个数size的值
7）操作次数modCount自增1.
剩余的慢慢看~