LinkedList的实现

package main.java.LinkedListdemo;import java.util.ConcurrentModificationException;import java.util.Iterator;import java.util.NoSuchElementException;/** * DateTime: 2016/11/4 15:02 * 功能： * 思路： */public class MyLinkedList<E> implements Iterable<E> {        /*           嵌套类  节点类         */    private static class Node<E>{        public E data;        public Node<E> prev;        public Node<E> next;        public Node(E e,Node<E> p,Node<E> q){            data=e;  prev=p;  next=q;        }    }    //类属性成员    private int size;    private int modCount=0;    private Node<E> beginMarker;    private Node<E> endMarker;    //构造函数    public MyLinkedList(){        doInit();    }    //清除函数    public void clear(){        doInit();    }    //新增函数    public void add(E value){        add(size(),value);    }    public void add(int index,E value){        addBefore(getNode(index,0,size()),value);    }    //清除函数    public void doInit(){        beginMarker=new Node<E>(null,null,null);        endMarker=new Node<E>(null,beginMarker,null);        beginMarker.next=endMarker;        size=0;        modCount++;    }    //链表元素个数    public int size(){        return this.size;    }    //判断是否为空    public boolean isEmpty(){        return 0==size();    }    //获得结点的数据    public E get(int index){        return getNode(index).data;    }    //设置结点数据并返回旧的值    public E set(int index,E value){        Node<E> p=getNode(index);        E oldValue=p.data;        p.data=value;        return oldValue;    }    //获得结点数据    private Node<E> getNode(int index){        return getNode(index,0,size()-1);    }    //获得结点数据    private Node<E> getNode(int index,int lower,int upper){        Node<E> p;        if(index<lower || index>upper){            throw new IndexOutOfBoundsException();        }        if(index<size()/2){            p=beginMarker.next;            for ( int i = 0; i < index; i++ ) {                p=p.next;            }        }else {            p=endMarker;            for ( int i = size(); i > index; i-- ) {                p=p.prev;            }        }        return p;    }    //在p结点之前添加节点    public void addBefore(Node<E> p,E value){        Node<E> node=new Node<E>(value,p.prev,p);        node.prev.next=node;        p.prev=node;        this.size++;        this.modCount++;    }    //移除结点的数据-根据下表    public E remove(int index){        return remove(getNode(index));    }    //移除结点的数据-根据结点    public E remove(Node<E> p){        p.next.prev=p.prev;        p.prev.next=p.next;        size--;        modCount++;        return p.data;    }    @Override    public Iterator<E> iterator() {        return new LinkedListIterator();    }    private class LinkedListIterator implements Iterator<E>{        private Node<E> current=beginMarker.next;//当前指针位置        private int expectedModCount=modCount;        private boolean okToRemove=false;        @Override        public boolean hasNext() {            return current!=endMarker;        }        @Override        public E next() {            if(modCount!=expectedModCount)                throw new ConcurrentModificationException();            if(!hasNext())                throw new NoSuchElementException();            E nextValue=current.data;            current=current.next;            okToRemove=true;            return nextValue;        }        @Override        public void remove() {            if(modCount!=expectedModCount)                throw new ConcurrentModificationException();            if(!okToRemove)                throw new IllegalStateException();            MyLinkedList.this.remove(current.prev);            expectedModCount++;            okToRemove=false;        }    }}

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测试：

package test.java;import main.java.LinkedListdemo.MyLinkedList;import java.util.Iterator;/** * DateTime: 2016/11/4 16:00 * 功能： * 思路： */public class MyLinkedListTest {    public static void main(String[] args) {        MyLinkedList linkedList=new MyLinkedList();        linkedList.add(1);        linkedList.add(2);        linkedList.add(3);        linkedList.add(4);        Iterator iterator=linkedList.iterator();        while ( iterator.hasNext() ){            System.out.println(iterator.next());        }    }}

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