Javaによるダイナミックチェーンテーブルの実装

public class LinkedList<E> {
    public class Node{
        public E e;
        public Node next;
        public Node(E e , Node next){
            this.e = e;
            this.next = next;
        }

        public Node(E e ){
            this(e,null);
        }

        public Node(){
            this(null,null);
        }

        @Override
        public String toString(){
            return e.toString();
        }
    }

    private Node dummyHead;
    private int size;

    public LinkedList(){
        dummyHead = new Node(null,null);
        size = 0;
    }

    //          
    public int getSize() {return size;}

    //        
    public boolean isEmpty(){return size == 0;}

    //          e
    public void addFirst(E e){
        add(0,e);
    }

    //    index(0-based)        e
    public void add(int index ,E e){
        if(index < 0 || index > size)
            throw new IllegalArgumentException("Add failed . Illegal index.");

            Node prev = dummyHead;
            for(int i = 0 ; i < index ; i ++)
                prev = prev.next;
//            Node node = new Node(e);
//            node.next = prev.next;
//            prev.next = node;
            prev.next = new Node(e,prev.next);
            size ++;

    }

    //           e
    public void addLast(E e){
        add(size , e);
    }

    //      index(0-based)      
    public E get(int index){
        if(index < 0 || index >=size)
            throw new IllegalArgumentException("Get failed. Illegal index");
        Node cur = dummyHead.next;
        for(int i = 0 ; i < index ;i ++)
            cur = cur.next;
        return cur.e;
    }

    //         
    public E getFirst(){
        return get(0);
    }
    //          
    public E getLast(){
        return get(size - 1);
    }

    //      index(0-based)      
    public void set(int index , E e){
        if(index < 0 || index >= size)
            throw new IllegalArgumentException("Set failed . Illegal index");
        Node cur = dummyHead.next;
        for(int i = 0; i < index ; i ++)
            cur = cur.next;
        cur.e = e;
    }

    //          e
    public boolean contains(E e){
        Node cur = dummyHead.next;
        while(cur != null){
            if(cur.e.equals(e))
                return true;
            cur = cur.next;
        }
        return false;
    }

    //      index(0-based)      ,        
    public E remove(int index){
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Remove failed.Index is illegal.");
        Node prev = dummyHead;
        for(int i = 0 ;i < index;i ++)
            prev = prev.next;

        Node retNode = prev.next;
        prev.next = retNode.next;
        retNode.next = null;
        size --;

        return retNode.e;
    }

    //           ，       
    public E removeFirst(){
        return remove(0);
    }
    //            ，       
    public E removeLast(){
        return remove(size - 1);
    }
    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();

        Node cur = dummyHead.next;
        while(cur != null){
            res.append(cur + "->");
            cur = cur.next;
        }

//               
//        for(Node cur = dummyHead.next;cur != null;cur = cur.next)
//            res.append(cur + "->");

        res.append("Null");
        return res.toString();

    }
}