voidlinkLast(E e) { final Node<E> l = last; final Node<E> newNode = newNode<>(l, e, null); last = newNode; if (l == null) first = newNode; else l.next = newNode; size++; modCount++; }
添加第一个节点过程如下
插入第二个节点
从这可以看出LinkedList是一个双向链表。
add(int index, E element)
指定位置插入一个节点。
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voidadd(int index, E element) { checkPositionIndex(index);
if (index == size) linkLast(element); else linkBefore(element, node(index)); }
调用checkPositionIndex函数,检查index是否符合规范。
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privatebooleanisPositionIndex(int index) { return index >= 0 && index <= size; }
privatevoidcheckPositionIndex(int index) { if (!isPositionIndex(index)) thrownewIndexOutOfBoundsException(outOfBoundsMsg(index)); }
private E unlinkFirst(Node<E> f) { // assert f == first && f != null; finalEelement= f.item; final Node<E> next = f.next; f.item = null; f.next = null; // help GC first = next; if (next == null) last = null; else next.prev = null; size--; modCount++; return element; }
private E unlinkLast(Node<E> l) { // assert l == last && l != null; finalEelement= l.item; final Node<E> prev = l.prev; l.item = null; l.prev = null; // help GC last = prev; if (prev == null) first = null; else prev.next = null; size--; modCount++; return element; }
publicintindexOf(Object o) { intindex=0; if (o == null) { for (Node<E> x = first; x != null; x = x.next) { if (x.item == null) return index; index++; } } else { for (Node<E> x = first; x != null; x = x.next) { if (o.equals(x.item)) return index; index++; } } return -1; }
publicbooleanremove(Object o) { if (o == null) { for (Node<E> x = first; x != null; x = x.next) { if (x.item == null) { unlink(x); returntrue; } } } else { for (Node<E> x = first; x != null; x = x.next) { if (o.equals(x.item)) { unlink(x); returntrue; } } } returnfalse; }
public E remove(int index) { checkElementIndex(index); return unlink(node(index)); }
publicvoidclear() { // Clearing all of the links between nodes is "unnecessary", but: // - helps a generational GC if the discarded nodes inhabit // more than one generation // - is sure to free memory even if there is a reachable Iterator for (Node<E> x = first; x != null; ) { Node<E> next = x.next; x.item = null; x.next = null; x.prev = null; x = next; } first = last = null; size = 0; modCount++; }
从头到尾删除,最后回到最初first和last都指向空的状态。
get(int index)
得到指定索引出的元素。
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public E get(int index) { checkElementIndex(index); return node(index).item; }
set(int index, E element)
设定指定索引处的值
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public E set(int index, E element) { checkElementIndex(index); Node<E> x = node(index); EoldVal= x.item; x.item = element; return oldVal; }
push(E e) & pop()
链表头插入和删除。
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publicvoidpush(E e) { addFirst(e); }
public E pop() { return removeFirst(); }
clone()
复制一份一样的链表。
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public Object clone() { LinkedList<E> clone = superClone();
// Put clone into "virgin" state clone.first = clone.last = null; clone.size = 0; clone.modCount = 0;
// Initialize clone with our elements for (Node<E> x = first; x != null; x = x.next) clone.add(x.item);
return clone; }
toArray()
转化为数组。
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public Object[] toArray() { Object[] result = newObject[size]; inti=0; for (Node<E> x = first; x != null; x = x.next) result[i++] = x.item; return result; }