全局变量
/*LinkedList size*/
transient int size = 0;
/**
* Pointer to first node.当前链头
* Invariant: (first == null && last == null) ||
* (first.prev == null && first.item != null)
*/
transient Node<E> first;
/**
* Pointer to last node.当前链尾
* Invariant: (first == null && last == null) ||
* (last.next == null && last.item != null)
*/
transient Node<E> last;
构造函数
public LinkedList() {
}
//Collection集合转成LinkedList
public LinkedList(Collection<? extends E> c) {
this();
addAll(c);
}
addAll Collection集合添加至LinkedList
public boolean addAll(Collection<? extends E> c) {
return addAll(size, c);
}
}
addAll 指定下标Collection集合添加至LinkedList
public boolean addAll(int index, Collection<? extends E> c){
checkPositionIndex(index);//检查index是否超过size
Object[] a = c.toArray();
int numNew = a.length;
//Collection本身为空集合则直接返回false
if (numNew == 0)
return false;
//定义上个节点,成功节点
Node<E> pred, succ;
//如果从链尾添加则链尾Last为pred,succ为null
if (index == size) {
succ = null;
pred = last;
} else {
//否则获取index所在Node节点,指向succ
succ = node(index);
//获取succ的上个节点指向pred
pred = succ.prev;
}
//迭代Collection的数组
for (Object o : a) {
@SuppressWarnings("unchecked")
E e = (E) o;
//创建新节点,并完成(pred<-e)左链关系
Node<E> newNode = new Node<>(pred, e, null);
//如果上个节点为空则newNode指向链头
if (pred == null)
first = newNode;
//否则完成(pred<=>e)双向链表
else
pred.next = newNode;
//重置pred,令新节点newNode指向pred,然后继续迭代
pred = newNode;
}
//链尾添加则将迭代完的pred指向last
if (succ == null) {
last = pred;
} else {
//否则建立双向链表pred<=>succ
pred.next = succ;
succ.prev = pred;
}
//更新size
size += numNew;
modCount++;
return true;
}
linkFirst 将E添加至链表头
private void linkFirst(E e) {
//备份原首元素至f
final Node<E> f = first;
//构造newNode,并指向为当前链表头first
final Node<E> newNode = new Node<>(null, e, f);
first = newNode;
//如果原首元素为空,则newNode也是链表尾
if (f == null)
last = newNode;
else
//否则建立双向链关系 f<=>newNode
f.prev = newNode;
size++;
modCount++;
}
linkFirst 将E添加至链表尾
void linkLast(E e) {
//备份尾元素
final Node<E> l = last;
//新建节点并完成单相关系l <= newNode
final Node<E> newNode = new Node<>(l, e, null);
//newNode成为新的链表尾
last = newNode;
//原链表尾为空,则newNode将成为新链表头
if (l == null)
first = newNode;
else
//否则建立双向链表关系 l <=> newNode
l.next = newNode;
size++;
modCount++;
}
linkBefore 将E添加到非空节点succ的前面
void linkBefore(E e, Node<E> succ) {
// assert succ != null;succ必须非空,否则空指针
//备份succ的上个节点prev
final Node<E> pred = succ.prev;
//建立新节点,并完成单向链关系pred<-newNode->succ
final Node<E> newNode = new Node<>(pred, e, succ);
//pred<-newNode<=>succ
succ.prev = newNode;
//pred为空则newNode成为链表头
if (pred == null)
first = newNode;
else
//否则建立双向关系pred<=>newNode<=>succ
pred.next = newNode;
size++;
modCount++;
}
linkBefore 将当前链头first拆除
private E unlinkFirst(Node<E> f) {
// assert f == first && f != null; //f必须为链表头并且非空
//备份原链头,并用于返回
final E element = f.item;
//获取原链次节点
final Node<E> next = f.next;
f.item = null;
f.next = null; // help GC
//原表链次节点成为当前链头first
first = next;
//如果原表链次节点为空,则尾也为空
if (next == null)
last = null;
else
//否则至链头的上节点为空
next.prev = null;
size--;
modCount++;
return element;
}
linkBefore 将当前链尾last拆除
private E unlinkLast(Node<E> l) {
// assert l == last && l != null;//参数l必须为链尾并且非空
//备份原链尾,并用于返回
final E element = l.item;
//原链尾上节点作为最新链尾last
final Node<E> prev = l.prev;
l.item = null;
l.prev = null; // help GC
last = prev;
//如果原表链尾二节点为空,则头也为空
if (prev == null)
first = null;
else
//否则至链头的下节点为空
prev.next = null;
size--;
modCount++;
return element;
}
linkBefore拆除非空节点
E unlink(Node<E> x) {
// assert x != null;//目标节点必须不为空
final E element = x.item;
final Node<E> next = x.next;
final Node<E> prev = x.prev;
//目标节点的上节点prev为空,即目标节点为链表头,所以next就成为链头
if (prev == null) {
first = next;
} else {
//否则为建立单向关系prev->next
prev.next = next;
x.prev = null;//拆除原节点prev关系
}
//目标节点的下节点next为空,即目标节点为链表尾,所以prev就成为链尾
if (next == null) {
last = prev;
} else {
//否则为建立双向关系prev<=>next
next.prev = prev;
x.next = null;//拆除原节点next关系
}
//除原节点item置空,help gc
x.item = null;
size--;
modCount++;
return element;
}
getFirst获取首节点元素
public E getFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return f.item;
}
getFirst获取尾节点元素
public E getLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return l.item;
}
removeFirst移除头节点元素
public E removeFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return unlinkFirst(f);
}
removeLast移除尾节点元素
public E removeLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return unlinkLast(l);
}
contains是否包含此元素
public boolean contains(Object o) {
return indexOf(o) != -1;
}
indexOf() 元素o所在链表下标
public int indexOf(Object o) {
int index = 0;
//o为空则迭代判断出首空元素,并返回下标
if (o == null) {
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null)
return index;
index++;
}
} else {
////o非空则迭代判断equals一致对象,并返回下标
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item))
return index;
index++;
}
}
return -1;
}
indexOf() 元素o所在链表最后下标
public int lastIndexOf(Object o) {
int index = size;
if (o == null) {
//反向迭代
//o为空则迭代判断出最后空元素,并返回下
for (Node<E> x = last; x != null; x = x.prev) {
index--;
if (x.item == null)
return index;
}
} else {
//o非空则迭代判断equals最后一致对象,并返回下标
for (Node<E> x = last; x != null; x = x.prev) {
index--;
if (o.equals(x.item))
return index;
}
}
return -1;
}
iremoveFirstOccurrence 移除首个元素o
public boolean removeFirstOccurrence(Object o) {
return remove(o);
}
remove 移除首个元素o
public boolean remove(Object o) {
if (o == null) {
//迭代出首空元素并完成拆链
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
//迭代出首元素并完成拆链
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item)) {
unlink(x);
return true;
}
}
}
return false;
}
clear 清空链
public void clear() {
// 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
//迭代完成拆链
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++;
}
get 获取所在下标元素
public E get(int index) {
checkElementIndex(index);//判断下标不能超过size
return node(index).item;
}
node 获取所在下标元素
Node<E> node(int index) {
// assert isElementIndex(index); ////判断下标不能超过size
//判断index实在链前半还是链后半,选择正向还是反向迭代
if (index < (size >> 1)) {
Node<E> x = first;
for (int i = 0; i < index; i++)
x = x.next;
return x;
} else {
Node<E> x = last;
for (int i = size - 1; i > index; i--)
x = x.prev;
return x;
}
}
removeLastOccurrence 拆除最后一个o所在链
//都是反向迭代，分null和equals
public boolean removeLastOccurrence(Object o) {
if (o == null) {
for (Node<E> x = last; x != null; x = x.prev) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
for (Node<E> x = last; x != null; x = x.prev) {
if (o.equals(x.item)) {
unlink(x);
return true;
}
}
}
return false;
}
jdk7相关
http://www.cnblogs.com/chenssy/p/3514524.html
