简单模拟列表存储

今天看了数据结构的链式存储，写了一个简单的例子：

  
  package com.test;



public class ImitateLinkedList<T> {
   
	
	private Node head ;
	private Node last;
	
	//定义一个内部的节点类
	private class Node{
	  private  T element;
	  private Node next;
	  public Node(T element,Node next){
		 this.element = element;
		 this.next = next;
	  }
	}
	
	//元素的个数
	private int size;
	

   	public ImitateLinkedList(){
   		head = last = null;
   	}
	
	public void addElement(T element){
		Node node = new Node(element,null);
		if(size == 0){
			head = last = node;
		}else {
			last.next = node;
			last = node;
		}
		size++;
	}
   	
	
   /**
    * 输出链式列表的元素
    */
   	public void show(){
   		Node current = head;
   		while(current != null){
   			System.out.println(current.element);
   			current = current.next;
   		}
   	}
	
   	
   	/**
   	 * 在指定的位置加入元素
   	 * @param index 索引位置
   	 * @param element
   	 */
   	public void addElement(int index,T element){
   		//
        if(index < 0){
        	index = 0;
        }
   		
   		Node node = new Node(element,null);
   		if(index == 0){
   			node.next = head;
   			head = node;
   			if(size == 0)
   			  last = node;
   		}else if(index >= size -1){
   			
   		
   			last.next = node;
   			last = node;
   		
   		}else {
   			Node previous = getNode(index -1);
   			Node next = getNode(index + 1);
   			node.next = previous.next;
   			previous.next = node;
   			
   		}
   		size ++;
   	}
   
   	//得到索引位置的节点
   	private  Node getNode(int index){
   		
   		if(index < 0 || index >= size){
			return null;
		}
   		Node current = head;
   		for(int i = 0 ;i < index ;i++){
   			current = current.next;
   		}
   		return current;
   	}
   	
   	
   	/*
   	 * 得到索引位置的元素
   	 */
   	public T get(int index){
   		checkIndex(index);
   		return getNode(index).element;
   	}
   
   	/**
   	 * 删除索引位置的元素
   	 * @param index
   	 */
   	
   	public void removeElement(int index){
   		if(size == 0){
 			throw new RuntimeException("没有可删除的元素");
   		}
   		checkIndex(index);
   		
   		if(index == 0){
   			head = head.next;
   			if(size == 1){
   				last = head;
   			}
   		}else if(index == size -1){
   		  Node node  =	 getNode(index - 1);
   		  node.next = null;
   		  last = node;
   		}else {
   			Node previous = getNode(index - 1);
   			Node removeNode = getNode(index);
   			previous.next = removeNode.next;
   		}
   		size --;
   	}
   /**
    * 
    * @param index 要删除的元素的索引
    */
	private void checkIndex(int index) {
		// TODO Auto-generated method stub
		if(index < 0 || index >= size){
			throw new IllegalArgumentException("invalid argument "+index);
		}
	}
   	
   	/**
   	 *  
   	 * @return 得到列表中最后一个元素
   	 */
	public T getLast(){
		return last == null ? null : last.element;
	}
	
	/**
	 *  得到列表中第一个元素
	 *   
	 */
	
	public T getFirst(){
		return head == null ? null : head.element;
	}
   	
	
	
	public void removeFirst(){
		if(size == 0){
			throw new RuntimeException("列表为空，不能删除元素");
		}
		this.removeElement(0);
	}
   	
	public void removeLast(){
		
		if(size == 0){
			throw new RuntimeException("列表为空，不能删除元素");
		}
		this.removeElement(size - 1);
	}

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

下面是测试代码

     package com.test;

import org.junit.Before;
import org.junit.Test;

public class ImitateLinkedListTest {
      
	private ImitateLinkedList<String> linkedList ;
	
	@Before
	public void setUp(){
		linkedList = new ImitateLinkedList<String>();
	}
	
	
	@Test
	public void testAddElement(){
		linkedList.addElement("asdf");
		linkedList.addElement("bdf");
		linkedList.addElement("cfsd");
		System.out.println(linkedList.getFirst());
		System.out.println(linkedList.getLast());
	}
	
	@Test
	public void testShow(){
		linkedList.addElement("asdf");
		linkedList.addElement("bdf");
		linkedList.addElement("cfsd");
		linkedList.show();
	}
	
	@Test
	public void testAddElementoverride(){
		linkedList.addElement(0,"asdf");
		linkedList.addElement(0,"bdf");
		linkedList.addElement(0,"cfsd");
		linkedList.show();
	}
	
	
	@Test
	public void testRemoveElement(){
		linkedList.addElement(0,"asdf");
		linkedList.addElement(1,"bdf");
		linkedList.addElement(2,"cfsd");
		linkedList.removeElement(0);
		linkedList.removeElement(0);
		linkedList.removeElement(0);
		linkedList.show();
		
	}
	
	@Test
	public void testGetFirst(){
		linkedList.addElement(0,"asdf");
		linkedList.addElement(1,"bdf");
		linkedList.addElement(2,"ahi");
		linkedList.addElement(1,"ghf");
		//linkedList.addElement("hello");
		//linkedList.addElement(0,"cfsd");
		///linkedList.removeElement(0);
		System.out.println(linkedList.getFirst());
		System.out.println(linkedList.getLast());
		linkedList.show();
	}
	
	
	@Test
	public void testremoveFirst(){
		linkedList.addElement(0,"asdf");
 	    linkedList.addElement(1,"ghf");
 	    linkedList.addElement("ccc");
		linkedList.removeFirst();
		linkedList.removeLast();
		System.out.println(linkedList.getFirst());
		System.out.println(linkedList.getLast());
		linkedList.show();
	}
	
	
	
}