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JDK 1.8 LinkedList解碼解讀
全局變量
/*LinkedList size*/
transient int size = 0;
/**
* Pointer to first node.當前鏈頭
* Invariant: (first == null && last == null) ||
* (first.prev == null && first.item != null)
*/
transient Node<E> first;
/**
* Pointer to last node.當前鏈尾
* Invariant: (first == null && last == null) ||
* (last.next == null && last.item != null)
*/
transient Node<E> last;
構造函數
public LinkedList() {
}
//Collection集合轉成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 指定下標Collection集合添加至LinkedList
public boolean addAll(int index, Collection<? extends E> c){
checkPositionIndex(index);//檢查index是否超過size
Object[] a = c.toArray();
int numNew = a.length;
//Collection本身為空集合則直接返回false
if (numNew == 0)
return false;
//定義上個節點,成功節點
Node<E> pred, succ;
//如果從鏈尾添加則鏈尾Last為pred,succ為null
if (index == size) {
succ = null;
pred = last;
} else {
//否則獲取index所在Node節點,指向succ
succ = node(index);
//獲取succ的上個節點指向pred
pred = succ.prev;
}
//迭代Collection的數組
for (Object o : a) {
@SuppressWarnings("unchecked")
E e = (E) o;
//創建新節點,並完成(pred<-e)左鏈關係
Node<E> newNode = new Node<>(pred, e, null);
//如果上個節點為空則newNode指向鏈頭
if (pred == null)
first = newNode;
//否則完成(pred<=>e)雙向鏈表
else
pred.next = newNode;
//重置pred,令新節點newNode指向pred,然後繼續迭代
pred = newNode;
}
//鏈尾添加則將迭代完的pred指向last
if (succ == null) {
last = pred;
} else {
//否則建立雙向鏈表pred<=>succ
pred.next = succ;
succ.prev = pred;
}
//更新size
size += numNew;
modCount++;
return true;
}
linkFirst 將E添加至鏈表頭
private void linkFirst(E e) {
//備份原首元素至f
final Node<E> f = first;
//構造newNode,並指向為當前鏈表頭first
final Node<E> newNode = new Node<>(null, e, f);
first = newNode;
//如果原首元素為空,則newNode也是鏈表尾
if (f == null)
last = newNode;
else
//否則建立雙向鏈關係 f<=>newNode
f.prev = newNode;
size++;
modCount++;
}
linkFirst 將E添加至鏈表尾
void linkLast(E e) {
//備份尾元素
final Node<E> l = last;
//新建節點並完成單相關係l <= newNode
final Node<E> newNode = new Node<>(l, e, null);
//newNode成為新的鏈表尾
last = newNode;
//原鏈表尾為空,則newNode將成為新鏈表頭
if (l == null)
first = newNode;
else
//否則建立雙向鏈表關係 l <=> newNode
l.next = newNode;
size++;
modCount++;
}
linkBefore 將E添加到非空節點succ的前麵
void linkBefore(E e, Node<E> succ) {
// assert succ != null;succ必須非空,否則空指針
//備份succ的上個節點prev
final Node<E> pred = succ.prev;
//建立新節點,並完成單向鏈關係pred<-newNode->succ
final Node<E> newNode = new Node<>(pred, e, succ);
//pred<-newNode<=>succ
succ.prev = newNode;
//pred為空則newNode成為鏈表頭
if (pred == null)
first = newNode;
else
//否則建立雙向關係pred<=>newNode<=>succ
pred.next = newNode;
size++;
modCount++;
}
linkBefore 將當前鏈頭first拆除
private E unlinkFirst(Node<E> f) {
// assert f == first && f != null; //f必須為鏈表頭並且非空
//備份原鏈頭,並用於返回
final E element = f.item;
//獲取原鏈次節點
final Node<E> next = f.next;
f.item = null;
f.next = null; // help GC
//原表鏈次節點成為當前鏈頭first
first = next;
//如果原表鏈次節點為空,則尾也為空
if (next == null)
last = null;
else
//否則至鏈頭的上節點為空
next.prev = null;
size--;
modCount++;
return element;
}
linkBefore 將當前鏈尾last拆除
private E unlinkLast(Node<E> l) {
// assert l == last && l != null;//參數l必須為鏈尾並且非空
//備份原鏈尾,並用於返回
final E element = l.item;
//原鏈尾上節點作為最新鏈尾last
final Node<E> prev = l.prev;
l.item = null;
l.prev = null; // help GC
last = prev;
//如果原表鏈尾二節點為空,則頭也為空
if (prev == null)
first = null;
else
//否則至鏈頭的下節點為空
prev.next = null;
size--;
modCount++;
return element;
}
linkBefore拆除非空節點
E unlink(Node<E> x) {
// assert x != null;//目標節點必須不為空
final E element = x.item;
final Node<E> next = x.next;
final Node<E> prev = x.prev;
//目標節點的上節點prev為空,即目標節點為鏈表頭,所以next就成為鏈頭
if (prev == null) {
first = next;
} else {
//否則為建立單向關係prev->next
prev.next = next;
x.prev = null;//拆除原節點prev關係
}
//目標節點的下節點next為空,即目標節點為鏈表尾,所以prev就成為鏈尾
if (next == null) {
last = prev;
} else {
//否則為建立雙向關係prev<=>next
next.prev = prev;
x.next = null;//拆除原節點next關係
}
//除原節點item置空,help gc
x.item = null;
size--;
modCount++;
return element;
}
getFirst獲取首節點元素
public E getFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return f.item;
}
getFirst獲取尾節點元素
public E getLast() {
final Node<E> l = last;
if (l == null)
throw new NoSuchElementException();
return l.item;
}
removeFirst移除頭節點元素
public E removeFirst() {
final Node<E> f = first;
if (f == null)
throw new NoSuchElementException();
return unlinkFirst(f);
}
removeLast移除尾節點元素
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所在鏈表下標
public int indexOf(Object o) {
int index = 0;
//o為空則迭代判斷出首空元素,並返回下標
if (o == null) {
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null)
return index;
index++;
}
} else {
////o非空則迭代判斷equals一致對象,並返回下標
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item))
return index;
index++;
}
}
return -1;
}
indexOf() 元素o所在鏈表最後下標
public int lastIndexOf(Object o) {
int index = size;
if (o == null) {
//反向迭代
//o為空則迭代判斷出最後空元素,並返回下
for (Node<E> x = last; x != null; x = x.prev) {
index--;
if (x.item == null)
return index;
}
} else {
//o非空則迭代判斷equals最後一致對象,並返回下標
for (Node<E> x = last; x != null; x = x.prev) {
index--;
if (o.equals(x.item))
return index;
}
}
return -1;
}
iremoveFirstOccurrence 移除首個元素o
public boolean removeFirstOccurrence(Object o) {
return remove(o);
}
remove 移除首個元素o
public boolean remove(Object o) {
if (o == null) {
//迭代出首空元素並完成拆鏈
for (Node<E> x = first; x != null; x = x.next) {
if (x.item == null) {
unlink(x);
return true;
}
}
} else {
//迭代出首元素並完成拆鏈
for (Node<E> x = first; x != null; x = x.next) {
if (o.equals(x.item)) {
unlink(x);
return true;
}
}
}
return false;
}
clear 清空鏈
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
//迭代完成拆鏈
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 獲取所在下標元素
public E get(int index) {
checkElementIndex(index);//判斷下標不能超過size
return node(index).item;
}
node 獲取所在下標元素
Node<E> node(int index) {
// assert isElementIndex(index); ////判斷下標不能超過size
//判斷index實在鏈前半還是鏈後半,選擇正向還是反向迭代
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 拆除最後一個o所在鏈
//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相關
https://www.cnblogs.com/chenssy/p/3514524.html
最後更新：2017-08-13 22:33:56