首先上一幅框架图：
package java.util;
public abstract class AbstractSequentialList<E> extends AbstractList<E> {
protected AbstractSequentialList() {//只有一个构造器
}
public E get(int index) {//获取指定位置的值
try {
return listIterator(index).next();//通过迭代器的方式
} catch (NoSuchElementException exc) {//找不到就抛出异常
throw new IndexOutOfBoundsException("Index: "+index);//这是个Runtime异常
}
}
public E set(int index, E element) {
try {
ListIterator<E> e = listIterator(index);//同样调用的listiterator
E oldVal = e.next();//记录
e.set(element);
return oldVal;//返回
} catch (NoSuchElementException exc) {
throw new IndexOutOfBoundsException("Index: "+index);
}
}
public void add(int index, E element) {
try {
listIterator(index).add(element);
} catch (NoSuchElementException exc) {
throw new IndexOutOfBoundsException("Index: "+index);
}
}
public E remove(int index) {
try {
ListIterator<E> e = listIterator(index);
E outCast = e.next();
e.remove();
return outCast;
} catch (NoSuchElementException exc) {
throw new IndexOutOfBoundsException("Index: "+index);
}
}
// Bulk Operations
public boolean addAll(int index, Collection<? extends E> c) {
try {
boolean modified = false;
ListIterator<E> e1 = listIterator(index);
Iterator<? extends E> e2 = c.iterator();
while (e2.hasNext()) {
e1.add(e2.next());
modified = true;
}
return modified;
} catch (NoSuchElementException exc) {
throw new IndexOutOfBoundsException("Index: "+index);
}
}
// Iterators
public Iterator<E> iterator() {
return listIterator();
}
public abstract ListIterator<E> listIterator(int index);//参数为索引位置。表示从哪开始遍历
}
public class LinkedList<E>
extends AbstractSequentialList<E>
implements List<E>, Deque<E>, Cloneable, java.io.Serializable
transient int size = 0;//集合大小(结点个数) transient Node<E> first;//头指针 transient Node<E> last;//尾指针前面说过，linkedList是通过双向链表实现，故而不需要有扩容的方法，因为结点是动态申请的。而这个结点的类型即为Node。下面看Node源码:
private static class Node<E> {
E item;//数据
Node<E> next;//后继指针
Node<E> prev;//前驱指针
Node(Node<E> prev, E element, Node<E> next) {
this.item = element;
this.next = next;
this.prev = prev;
}
}
public LinkedList() {}
public LinkedList(Collection<? extends E> c) {
this();
addAll(c);
}
private void linkFirst(E e) {//插到头部
final Node<E> f = first;
//创建一个新结点，前驱为空，后继为f(也就是当前的头结点)
final Node<E> newNode = new Node<>(null, e, f);//注意这种泛型的写法也是可以的
first = newNode;//头指针指向新结点
if (f == null)//链表为空时
last = newNode;//尾指针指向新结点
else//否则
f.prev = newNode;//让f的前驱指向新结点
size++;
modCount++;
}
void linkLast(E e) {//插到尾部
final Node<E> l = last;//临时变量记录尾结点
final Node<E> newNode = new Node<>(l, e, null);//创建新结点，前驱为l
last = newNode;//更新尾指针
if (l == null)//如果链表为空
first = newNode;
else
l.next = newNode;
size++;
modCount++;//用于快速失败机制
}
void linkBefore(E e, Node<E> succ) {//将e插入succ之前
// assert succ != null;//调用者需要保证succ不为空
final Node<E> pred = succ.prev;//记录succ的前驱
final Node<E> newNode = new Node<>(pred, e, succ);//新结点的前驱指向succ的前驱，新结点的后继指向succ
succ.prev = newNode;//succ的前驱指向新结点
if (pred == null)//succ为头结点
first = newNode;//更改头指针
else
pred.next = newNode;//否则succ的前驱的后继指向新结点
size++;
modCount++;
}
private E unlinkFirst(Node<E> f) {//干掉头结点f
// assert f == first && f != null;
final E element = f.item;
final Node<E> next = f.next;
f.item = null;
f.next = null; // help GC
first = next;//更改头指针
if (next == null)
last = null;
else
next.prev = null;
size--;
modCount++;
return element;
}
private E unlinkLast(Node<E> l) {//干掉尾结点l
// assert l == last && l != null;
final E element = 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;
}
E unlink(Node<E> x) {//干掉一个普通结点x
// assert x != null;
final E element = x.item;//记录这个结点值
final Node<E> next = x.next;//记录下一个结点
final Node<E> prev = x.prev;//记录上一个结点
if (prev == null) {//上一个结点为空
first = next;
} else {
prev.next = next;//上一个结点的下一个指向下一个结点
x.prev = null;
}
if (next == null) {
last = prev;
} else {
next.prev = prev;//下一个结点的上一个指向上一个
x.next = null;
}
x.item = null;
size--;
modCount++;
return element;
}有了这些基本函数之后，实现其他操作就方便了。比如这些： public void addFirst(E e) {
linkFirst(e);
}
public void addLast(E e) {
linkLast(e);
}
public boolean add(E e) {
linkLast(e);
return true;
}再看这个remove方法：
public boolean remove(Object o) {
if (o == null) {
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 void clear() {
for (Node<E> x = first; x != null; ) {
Node<E> next = x.next;//临时变量记录待删除结点的下一个
x.item = null;
x.next = null;
x.prev = null;
x = next;
}
first = last = null;
size = 0;
modCount++;
}下面的函数封装了索引链表位置的操作： Node<E> node(int index) {
// assert isElementIndex(index);
if (index < (size >> 1)) {//判断待索引的大致位置
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;
}
}
public ListIterator<E> listIterator(int index) {
checkPositionIndex(index);
return new ListItr(index);
}
private class ListItr implements ListIterator<E>
private Node<E> next;
ListItr(int index) {
// assert isPositionIndex(index);
next = (index == size) ? null : node(index);
nextIndex = index;
}
public Iterator<E> descendingIterator() {
return new DescendingIterator();
}【源码】LinkedList源码剖析,布布扣,bubuko.com
原文：http://blog.csdn.net/chdjj/article/details/38447015