Java代码实现一个链表结构

public class MyList<AnyType>  {  
private class Node<AnyType>{  
public  Node<AnyType> pre;  
public  Node<AnyType> next;  
public  AnyType      data;  
public Node(AnyType d, Node<AnyType>p, Node<AnyType> n){}  
public Node(){}  
}  
private int theSize;  
private Node<AnyType> Header;  
private Node<AnyType> Tail;  
public MyList(){}  
public void add(AnyType item){}  
public boolean isEmpty(){}  
public int size(){}  
public AnyType get( int idx){}  
public void print(){}  
}  
/*Node<AnyType>类定义了双向链表中节点的结构，它是一个私有类，而其属性和构造函数都是公有的，这样，其父类可以直接访问其属性，而外部类根本不知道Node类的存在。Data是节点中的数据与，pre指向前一个Node节点，next指向后一个Node节点。其构造函数的实现如下，不解释： 
View Code*/  
public Node(AnyType d, Node<AnyType>p, Node<AnyType> n){  
this.data = d;  
this.pre = p;  
this.next = n;  
}  
public Node(){  
  this.data = null;  
  this.pre = null;  
  this.next = null;  
}  
/*下面我们看一下链表的构造函数实现： 
View Code*/  
public MyList(){  
  theSize = 0;  
  Header = new Node<AnyType>(null,null,null);  
  Tail   =  new Node<AnyType>(null,Header,null);  
  Header.next = Tail;  
}  
/*我们构造了一个带有头、尾节点的双向链表，头节点的Next指向尾节点，为节点的pre指向头节点。链表长度起始为0。 
继续贴上链表类其它方法的实现，不解释了，应该比较清楚：*/  
//View Code  
public void add(AnyType item){  
  Node<AnyType> aNode = new Node<AnyType>(item,null,null);  
  Tail.pre.next = aNode;  
  aNode.pre = Tail.pre;  
  aNode.next = Tail;  
  Tail.pre = aNode;  
  theSize++;  
}  
public boolean isEmpty(){  
    return ( theSize == 0);  
}  
public int size(){  
   return theSize;  
}  
public AnyType get( int idx){  
  if(idx > theSize-1 || idx < 0)  
     throw new IndexOutOfBoundsException();  
     Node<AnyType> current = new Node<AnyType>(null,Header,null);  
     for(int i = 0; i<idx; i++)  
         current = current.next;  
     return current.data;  
}  
public void print(){  
  Node<AnyType> current = Header.next;  
  while(current.next != null){  
   //如果AnyType是你自己定义 //的数据类型，那么请务必提供  
   //一个toString方法，要么就不  
   //要在链表里实现print方法。  
  System.out.println(current.data.toString());   
      current = current.next;  
}  
}