双链表---LinkedList的重写

重写Linkedlist类，改写为MyLinkedList,未继承Iterable类。

public class MyLinkedList<AnyType>  {    private int theSize;    private Node<AnyType> beginMarker;    private Node<AnyType> endMarker;    private static class Node<AnyType>{          //定义匿名类Nodepublic Node(AnyType d,Node<AnyType> p,Node<AnyType> n){this.data=d;this.prev=p;this.next=n;}public AnyType data;public Node<AnyType> prev;public Node<AnyType> next;}public MyLinkedList(){                         //构造方法beginMarker=new Node<AnyType>(null,null,null);endMarker=new Node<AnyType>(null,beginMarker,null);beginMarker.next=endMarker;theSize=0;}public int size(){                     //单链表cdureturn theSize;}public boolean isEmploy(){               //判断长度return size()==0;}public Node<AnyType> getNode(int idx){             //返回idx对应的结点Node<AnyType> p;if(idx<0||idx>size())            throw new IndexOutOfBoundsException(  );if(idx<size()/2){p=beginMarker.next;for(int i=0;i<idx;i++)p=p.next;}else{p=endMarker;for(int i=size();i>idx;i--)p=p.prev;} return p;    }public AnyType get(int idx){     //返回idx位置的数据return getNode(idx).data;}public AnyType set(int idx,AnyType newVal){Node<AnyType> p=getNode(idx);AnyType oldVal=get(idx);p.data=newVal;return oldVal;}public boolean add(AnyType x){     //插入元素add(size(),x);return true;}private void addBefore(Node<AnyType> p,AnyType x){Node<AnyType> newNode=new Node<AnyType>(x,p.prev,p);newNode.prev.next=newNode;p.prev=newNode;theSize++;}public void add(int idx,AnyType x){Node<AnyType> p;p=getNode(idx);addBefore(p,x);}public AnyType remove(int idx){              //删除元素return remove(getNode(idx));}public AnyType remove(Node<AnyType> p){p.next.prev=p.prev;p.prev.next=p.next;theSize--;return p.data;}public static void main(String[] args) {      //验证部分MyLinkedList<String> La=new MyLinkedList<String>();La.add("aaa");La.add("bbb");La.add("ccc");La.add("ddd");La.add("eee");for(int i=0;i<La.size();i++){System.out.println(i+": "+La.getNode(i).data);}System.out.println("......................");La.add(2,"fff");La.remove(0);La.set(4,"ggg");for(int i=0;i<La.size();i++){System.out.println(i+": "+La.get(i));}}}