public class LinkedList<E>extends AbstractSequentialList<E>implements List<E>, Deque<E>, Cloneable, java.io.Serializable

LinkedList繼承自AbstractSequenceList、實(shí)現(xiàn)了List及Deque接口。
AbstractSequenceList提供List接口的骨干實(shí)現(xiàn),以減少實(shí)現(xiàn)List接口的復(fù)雜度。
Deque是Queue的一個(gè)子接口，雙向隊(duì)列是指該隊(duì)列兩端的元素既能入隊(duì)(offer)也能出隊(duì)(poll)。

• LinkedList的屬性

transient int size = 0; //存儲(chǔ)元素的個(gè)數(shù) transient Node<E> first; //頭節(jié)點(diǎn) //jdk1.6 Entry<E> header = new Entry<E>(null, null, null); transient Node<E> last; //尾節(jié)點(diǎn) private static class Node<E> {E item;Node<E> next;Node<E> prev;Node(Node<E> prev, E element, Node<E> next) {this.item = element;this.next = next;this.prev = prev;}}

• LinkedList的構(gòu)造方法

public LinkedList() { //jdk1.6 header.next = header.previous = header;帶有頭結(jié)點(diǎn)雙向循環(huán)鏈表} //jkd1.7+ 不帶頭節(jié)點(diǎn)的雙向鏈表public LinkedList(Collection<? extends E> c) {this();addAll(c); //conllection 轉(zhuǎn)換成數(shù)組 for循環(huán)添加}

• LinkedList的方法
  add方法

public boolean add(E e) {linkLast(e); //直接添加到尾部return true;}public void add(int index, E element) {checkPositionIndex(index); //檢查下標(biāo)if (index == size)linkLast(element); //是在尾部添加else //中間插入linkBefore(element, node(index)); //查找index處的節(jié)點(diǎn)，把新節(jié)點(diǎn)添加到它的前面}private void checkPositionIndex(int index) {if (!isPositionIndex(index)) //非真就拋異常throw new IndexOutOfBoundsException(outOfBoundsMsg(index));}private boolean isPositionIndex(int index) {return index >= 0 && index <= size; //當(dāng)于等于0且小于等于當(dāng)前size的大小}void linkLast(E e) { //分2種情況解釋 第一次添加 非第一次添加final Node<E> l = last; //第一次添加last為null 第二次添加last不是null final Node<E> newNode = new Node<>(l, e, null); //假如第一次添加個(gè)String類型的“1” 第二次添加個(gè)String類型的“2”last = newNode; //newNode的item是“1”，newNode.next=null newNode的item是“2”，newNode.next=null if (l == null) //nowNode.prev=null,并將成員變量last指向newNode nowNode.prev="1"first = newNode; //因?yàn)槭堑谝淮翁砑?#xff0c;l也是null， 第二次添加，l不是nullelse //將成員變量frist指向newNode 將當(dāng)前添加的節(jié)點(diǎn)指向上一個(gè)節(jié)點(diǎn)的next屬性l.next = newNode; //添加后是[null]["1"][null] [null]["1"]["2"][null]size++; // prve item next prve item nextmodCount++;}void linkBefore(E e, Node<E> succ) {// assert succ != null;final Node<E> pred = succ.prev; //獲取succ前面的一個(gè)節(jié)點(diǎn)final Node<E> newNode = new Node<>(pred, e, succ); //新建一個(gè)節(jié)點(diǎn)，前面指向succ前面一個(gè)借點(diǎn)，后面指向succsucc.prev = newNode; //succ前面的節(jié)點(diǎn)指向新建的節(jié)點(diǎn)if (pred == null) //如果succ前面的節(jié)點(diǎn)為空,新建的節(jié)點(diǎn)則為頭節(jié)點(diǎn)first = newNode;elsepred.next = newNode; //否則就將前面節(jié)點(diǎn)的下一點(diǎn)指向新建的節(jié)點(diǎn)size++;modCount++;}

remove方法

public boolean remove(Object o) { //判斷要?jiǎng)h除的元素是不是nullif (o == null) { //從首節(jié)點(diǎn)開始循環(huán)，然后刪除for (Node<E> x = first; x != null; x = x.next) {if (x.item == null) {unlink(x);return true;}}} else {for (Node<E> x = first; x != null; x = x.next) {if (o.equals(x.item)) {unlink(x);return true;}}}return false;}public E remove(int index) {checkElementIndex(index); //檢查數(shù)組下標(biāo)越界return unlink(node(index));}private void checkElementIndex(int index) {if (!isElementIndex(index))throw new IndexOutOfBoundsException(outOfBoundsMsg(index));}private boolean isElementIndex(int index) {return index >= 0 && index < size;}Node<E> node(int index) {// assert isElementIndex(index);if (index < (size >> 1)) { //假如index小于size的一半Node<E> x = first; //從頭開始循環(huán)for (int i = 0; i < index; i++)x = x.next;return x;} else { //否則從結(jié)尾開始循環(huán)Node<E> x = last;for (int i = size - 1; i > index; i--)x = x.prev;return x;}}E unlink(Node<E> x) {// assert x != null; //假如LinkerList有這么一組數(shù)據(jù)[1,2,3,4,5] remove index是0的數(shù)據(jù)final E element = x.item; //則節(jié)點(diǎn)是1 x.item = 1 next = 2 prev = 3 final Node<E> next = x.next;final Node<E> prev = x.prev;if (prev == null) { //prev ==null，2現(xiàn)在就是首節(jié)點(diǎn)了first = next; //這里要注意一點(diǎn)，假如有這么一組數(shù)據(jù)[1,2,3,null,null,null,8,9]，remove index是4} else { //item prve next 分別為空 ，只是表示指向的內(nèi)容是nullprev.next = next; //假如刪除的不是頭結(jié)點(diǎn)，將下個(gè)節(jié)點(diǎn)指向上個(gè)節(jié)點(diǎn)的下個(gè)節(jié)點(diǎn)x.prev = null; //將刪除的節(jié)點(diǎn)的上個(gè)節(jié)點(diǎn)指向設(shè)置為null}if (next == null) { last = prev;} else { //接著[1,2,3,4,5]來解釋next.prev = prev; //假如刪除的不是尾結(jié)點(diǎn)，prve此時(shí)是null了，2是首節(jié)點(diǎn)，2.prev = null;x.next = null; //將刪除的節(jié)點(diǎn)的下個(gè)節(jié)點(diǎn)指向設(shè)置為null}x.item = null; //將刪除的節(jié)點(diǎn)也置為nullsize--;modCount++;return element;}

set

public E set(int index, E element) {checkElementIndex(index); //檢查數(shù)據(jù)下標(biāo)越界Node<E> x = node(index); //獲取要修改坐標(biāo)的元素E oldVal = x.item; //獲取這個(gè)坐標(biāo)元素的item屬性x.item = element; //將要修改元素的item屬性引用指向elementreturn oldVal;}

get

public E get(int index) {checkElementIndex(index); //檢查數(shù)據(jù)下標(biāo)越界return node(index).item; //for循環(huán)來取}

Iterator

private class ListItr implements ListIterator<E> { //正序迭代private Node<E> lastReturned = null;private Node<E> next;private int nextIndex;private int expectedModCount = modCount;ListItr(int index) {next = (index == size) ? null : node(index);nextIndex = index;}public boolean hasNext() {return nextIndex < size;}public E next() {checkForComodification();if (!hasNext())throw new NoSuchElementException();lastReturned = next;next = next.next;nextIndex++;return lastReturned.item;}public boolean hasPrevious() {return nextIndex > 0;}public E previous() {checkForComodification();if (!hasPrevious())throw new NoSuchElementException();lastReturned = next = (next == null) ? last : next.prev;nextIndex--;return lastReturned.item;}public int nextIndex() {return nextIndex;}public int previousIndex() {return nextIndex - 1;}public void remove() {checkForComodification();if (lastReturned == null)throw new IllegalStateException();Node<E> lastNext = lastReturned.next;unlink(lastReturned);if (next == lastReturned)next = lastNext;elsenextIndex--;lastReturned = null;expectedModCount++;}public void set(E e) {if (lastReturned == null)throw new IllegalStateException();checkForComodification();lastReturned.item = e;}public void add(E e) {checkForComodification();lastReturned = null;if (next == null)linkLast(e);elselinkBefore(e, next);nextIndex++;expectedModCount++;}final void checkForComodification() {if (modCount != expectedModCount)throw new ConcurrentModificationException();}}private class DescendingIterator implements Iterator<E> { //倒序迭代private final ListItr itr = new ListItr(size());public boolean hasNext() {return itr.hasPrevious();}public E next() {return itr.previous();}public void remove() {itr.remove();}}

總結(jié)

linkedList基于雙向鏈表實(shí)現(xiàn)，有序，允許為null,沒有固定容量，不需要擴(kuò)容。
其中的每個(gè)對(duì)象包含數(shù)據(jù)的同時(shí)還包含指向鏈表中前一個(gè)與后一個(gè)元素的引用。

轉(zhuǎn)載于:https://www.cnblogs.com/Ch1nYK/p/8589415.html

總結(jié)

以上是生活随笔為你收集整理的LinkedList源码详解的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。