/**
* Links e as last element.
*/void linkLast(E e) {
final Node<E> l = last;
final Node<E> newNode = new Node<>(l, e, null);
last = newNode;
if (l == null)
first = newNode;
else
l.next = newNode;
size++;
modCount++;
}
privatevoid checkPositionIndex(intindex) {
if (!isPositionIndex(index))
thrownew IndexOutOfBoundsException(outOfBoundsMsg(index));
}
privateboolean isPositionIndex(intindex) {
returnindex >= 0 && index <= size;
}
进行位置插入:
/**
* Inserts element e before non-null Node succ.
*/void linkBefore(E e, Node<E> succ) {
// assert succ != null;final Node<E> pred = succ.prev;
final Node<E> newNode = new Node<>(pred, e, succ);
succ.prev = newNode;
if (pred == null)
first = newNode;
else
pred.next = newNode;
size++;
modCount++;
}
知道Node的各个意思之后,代码就非常简单易懂了。
addAll方法最终使用的是一种方法:
publicbooleanaddAll(Collection< extends E> c) {
return addAll(size, c);
}
publicbooleanaddAll(int index, Collection< extends E> c) {
checkPositionIndex(index);
Object[] a = c.toArray();
int numNew = a.length;
if (numNew == 0)
returnfalse;
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++;
returntrue;
}
/**
* Links e as first element.
*/privatevoidlinkFirst(E e) {
final Node<E> f = first;
final Node<E> newNode = new Node<>(null, e, f);
first = newNode;
if (f == null)
last = newNode;
else
f.prev = newNode;
size++;
modCount++;
}