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Node
		public 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cdu
		return 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));
		}
	}

}