java.util.LinkedList

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类定义

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

transient int size = 0 ;  //链表初始容量为0transient Node<E> first; //指向第一个节点的指针transient Node<E> last; //指向最后一个节点的指针

方法

public linkedList(){} //实例化一个空的链表public LinkedList(Collection<? extends E> c){ //将集合c插入链表 this(); addAll(c);}

私有方法

//将e插到链表首位private void linkFirst(E e){final Node<E> f = first;final Node<E> newNode = new Node<E>(null,e,f);first = newNode;if(f==null)last=newNode;else f.prev=newNode;size++;modCount++;}//将e插入到链表最后void linkLast(E e){ final Node<E> l = last; final Node<E> newNode = new Node<E>(l,e,null); last=newNode; if(l==null)first=newNode; else l.next=newNode; size++; modCount++;}//在指针succ之前插入一个元素e,succ必须为非空指针void linkBefore(E e, Node<E> succ){ final Node<E> pred=succ.prev; final Node<E> newNode = new Node<>(pred,e,succ); if(pred==null) first=newNode; else pred.next=newNode; size++; modCount++;}//删除第一个节点,f==first&&f!=nullprivate E unlinkFirst(Node<E> f){ final E element = f.item; final Node<E> next =f.next; f.item=null; f.next=null; first=next; if(next==null)last=null; else next.prev=null; size--; modCount++; return element;}//删除最后一个节点，l==last&&l!=nullprivate E unlinkLast(Node<E> l){final E element = l.item;final Node<E> prev = l.prev;l.item=null;l.prev=null;last=prev;if(prev==null)first=null;else prev.next=null;size--;modCount++;return element;}//删除节点xE  unlink(Node<E> x){final E element = x.item;final Node<E> next = x.next;final Node<E> prev = x.prev;if(prev==null)first=next;else {  prev.next=next;  x.prev=null;}if(next==null){ last==prev;}else{next.prev=prev;x.next=null;}x.item=null;size--;modCount++;return element;}//获取链表头元素public E getFirst(){final Node<E> f = first;if(f==null)throw new NoSuchElementException();return f.item;}//获取链表尾元素public E getLast(){final Node<E> l = last;if(l==null)throw new NoSuchElementException();return l.item;}//删除第一个元素public E removeFirst(){final Node<E> f = first;if(f==null)throw new NoSuchElementException();return unlinkFirst(f);}//删除最后一个元素public E removeLast(){final Node<E> l = last;if(last==null)throw new NoSuchElementException();unlinkLast(l);}//在链表头插入元素public void addFirst(E e){ linkFirst(e);}public void addLast(E e) {        linkLast(e);    }    //是否包含元素opublic boolean contains(Object o) {        return indexOf(o) != -1;    }    //返回链表大小 public int size() {        return size;    }    //添加一个元素（在链表末尾）public boolean add(E e) {        linkLast(e);        return true;    }    //从头遍历链表，删除第一个遇到的与o相同的元素,该遍历用for循环遍历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;    }//将集合c插入到链表末尾public boolean addAll(Collection<? extends E> c) {        return addAll(size, c);    }//在链表指定位置插入集合cpublic boolean addAll(int index, Collection<? extends E>c){checkPositionIndex(index);Object[] a = c.toArray();int numNew = a.length;if(newNew == 0)return false;Node<E> pred,succ;if(index==size){succ=null;pred=last;}else{ succ=node(index); pred=succ.prev;}for(Object o :a){Node<E> newNode = new Node<>(pred,e,null);if(pred==null)first=newNode;else pred.next=newNode;pred=newNode;}if(succ==null)last=pred;else{pred.next=succ;succ.prev=pred;}size+=newNew;modCount++;return true;}//清空链表public void clear(){for(Node<E> x=first;x!=null;){ Node<E> next=x.next; x.item=null; x.prev=null; x.next=null; x=next;}first=last=null;size=0;modCount++;}//获取指定位置的元素pubilc E get(int index){ checkElementIndex(index); return nod(index).item;}//替换指定位置的元素,返回替换之前该位置的值public E set(int index, E element) {        checkElementIndex(index);        Node<E> x = node(index);        E oldVal = x.item;        x.item = element;        return oldVal;    }//在指定位置插入一个元素public void add(int index, E element) {        checkPositionIndex(index);        if (index == size)            linkLast(element);        else            linkBefore(element, node(index));    }//删除指定的元素,并返回该元素public E remove(int index) {        checkElementIndex(index);        return unlink(node(index));    }//判断index位置是否存在private boolean isElementIndex(int index){return index>=0&&index<size;}//针对迭代器或者add操作，判断Index是否是一个合法的位置private boolean isPositionIndex(int index){return index>=0 && index<= size;}//返回越界提示信息private String outOfBoundsMsg(int index) {        return "Index: "+index+", Size: "+size;    }//检查Index是否是一个合法的元素位置private void checkElementIndex(int index) {        if (!isElementIndex(index))            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));    }//检查index是否是一个合法的增加元素位置private void checkPositionIndex(int index) {        if (!isPositionIndex(index))            throw new IndexOutOfBoundsException(outOfBoundsMsg(index));    }//返回第一个元素o的位置，没有则返回-1public int indexOf(Object o) {        int index = 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;    }//返回o在链表中最后出现的位置public int lastIndexOf(Object o) {        int index = size;        if (o == null) {            for (Node<E> x = last; x != null; x = x.prev) {                index--;                if (x.item == null)                    return index;            }        } else {            for (Node<E> x = last; x != null; x = x.prev) {                index--;                if (o.equals(x.item))                    return index;            }        }        return -1;    }*********************以下是队列操作****************************//返回队列头元素public E peek(){final Node<E> f = first;return (f == null) ? null : f.item;}//返回头节点元素public E element() {        return getFirst();    }//删除并返回头节点元素public E poll() {        final Node<E> f = first;        return (f == null) ? null : unlinkFirst(f);    }//删除并返回头节点元素public E remove() {        return removeFirst();    }//将具体元素插入表尾 public boolean offer(E e) {        return add(e);    }//将元素插入表头  public boolean offerFirst(E e) {        addFirst(e);        return true;    }//将具体元素插入表尾public boolean offerLast(E e) {        addLast(e);        return true;    }//返回但不删除表头元素public E peekFirst() {        final Node<E> f = first;        return (f == null) ? null : f.item;     }//返回但不删除表尾元素public E peekLast() {        final Node<E> l = last;        return (l == null) ? null : l.item;    }//删除并返回表头元素public E pollFirst() {        final Node<E> f = first;        return (f == null) ? null : unlinkFirst(f);    }//删除并返回表尾元素public E pollLast() {        final Node<E> l = last;        return (l == null) ? null : unlinkLast(l);    }****************栈操作********************//压栈,栈顶为表头 public void push(E e) {        addFirst(e);    }//出栈public E pop() {        return removeFirst();    }//删除第一次遇到的opublic boolean removeFirstOccurrence(Object o) {        return remove(o);    }//删除最后一次遇到的opublic 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;    }//返回链表的迭代器public ListIterator<E> listIterator(int index) {        checkPositionIndex(index);        return new ListItr(index);    }//返回链表的倒序迭代器（从表尾遍历到表头）public Iterator<E> descendingIterator() {        return new DescendingIterator();    }//返回包含链表所有元素的数组public Object[] toArray() {        Object[] result = new Object[size];        int i = 0;        for (Node<E> x = first; x != null; x = x.next)            result[i++] = x.item;        return result;    }    public <T> T[] toArray(T[] a) {        if (a.length < size)            a = (T[])java.lang.reflect.Array.newInstance(                                a.getClass().getComponentType(), size);        int i = 0;        Object[] result = a;        for (Node<E> x = first; x != null; x = x.next)            result[i++] = x.item;        if (a.length > size)            a[size] = null;        return a;    }

私有类Node

//定义链表节点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;        }    }//定义链表的迭代器private class ListItr implements ListIterator<E> {        private Node<E> lastReturned = null;        private Node<E> next;        private int nextIndex;        private int expectedModCount = modCount;        ListItr(int index) {            // assert isPositionIndex(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;            else                nextIndex--;            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);            else                linkBefore(e, next);            nextIndex++;            expectedModCount++;        }        final void checkForComodification() {            if (modCount != expectedModCount)                throw new ConcurrentModificationException();        }    }private class DescendingIterator implements Iterator<E> {        private final ListItr itr = new ListItr(size());        public boolean hasNext() {            return itr.hasPrevious();        }        public E next() {            return itr.previous();        }        public void remove() {            itr.remove();        }    }

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