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 stubif(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;}}

     package com.test;import org.junit.Before;import org.junit.Test;public class ImitateLinkedListTest {      private ImitateLinkedList<String> linkedList ;@Beforepublic void setUp(){linkedList = new ImitateLinkedList<String>();}@Testpublic void testAddElement(){linkedList.addElement("asdf");linkedList.addElement("bdf");linkedList.addElement("cfsd");System.out.println(linkedList.getFirst());System.out.println(linkedList.getLast());}@Testpublic void testShow(){linkedList.addElement("asdf");linkedList.addElement("bdf");linkedList.addElement("cfsd");linkedList.show();}@Testpublic void testAddElementoverride(){linkedList.addElement(0,"asdf");linkedList.addElement(0,"bdf");linkedList.addElement(0,"cfsd");linkedList.show();}@Testpublic 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();}@Testpublic 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();}@Testpublic 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();}}