java开始到熟悉103-104

本次内容：linkedlist（）

此次是承接上次arraylist（），自己实现linkedlist（）（内容较少）

 package list;
 /**
  * 自定义linkedlist类
  * @author acer
  *
  */
 public class mylinkedlist {
     private Node first;
     private Node last;
     private int size;
     public void add(Object obj)
     {
         Node n=new Node();
         if(first==null)
         {
             n.setPrevious(null);
             n.setObj(obj);
             n.setNext(null);
             first=n;
             last=n;
         }
         else
         {
             n.setPrevious(last);
             n.setObj(obj);
             n.setNext(null);
             last.setNext(n);
             last=n;
         }
         size++;
     }
     public void add(int index,Object obj)
     {
         Node temp=null;
         Node newNode=new Node();
         newNode.setObj(obj);
         if(first!=null)
         {
             temp=first;
             for(int i=0;i<index;i++)
             {
                 temp=temp.getNext();
             }
         }
         newNode.setPrevious(temp.getPrevious());
         temp.getPrevious().setNext(newNode);
         newNode.setNext(temp);
         temp.setPrevious(newNode);
         size++;

     }
     public Object get(int index)
     {
         rangeCheck(index);
         Node temp=null;
         if(first!=null)
         {
             temp=first;
             for(int i=0;i<index;i++)
             {
                 temp=temp.getNext();
             }
         }
         return temp.getObj();
     }
     public void removefirst()
     {
         Node temp=null;
         temp=first;
         temp=temp.getNext();
         temp.setPrevious(null);
         first.setNext(null);
         first=temp;
     }
     public void remove(int index)
     {
         rangeCheck(index);
         Node temp=null;
         if(first!=null)
         {
             temp=first;
             for(int i=0;i<index;i++)
             {
                 temp=temp.getNext();
             }
         }
         if(temp!=null)
         {
             Node pre=temp.getPrevious();
             Node ne=temp.getNext();
             pre.setNext(ne);
             ne.setPrevious(pre);
             size--;
         }

     }
     public void rangeCheck(int index)
     {
         if(index<0||index>=size)
         {
             try {
                 throw new Exception();
             } catch (Exception e) {
                 e.printStackTrace();
             }
         }
     }
     public int size()
     {
         return size;
     }
     public static void main(String[] args)
     {
         mylinkedlist list=new mylinkedlist();
         list.add("aaa");
         list.add("bbb");
         list.add("ccc");
         list.add("ddd");
         System.out.println(list.size());
         System.out.println(list.get(1));
         list.removefirst();
         System.out.println(list.get(0));
     }
 }

 class Node
 {
     private Node previous;
     private Object obj;
     private Node next;
     public Node()
     {
     }
     public Node(Node previous, Object obj, Node next) {
         super();
         this.previous = previous;
         this.obj = obj;
         this.next = next;
     }
     public Node getPrevious() {
         return previous;
     }
     public void setPrevious(Node previous) {
         this.previous = previous;
     }
     public Object getObj() {
         return obj;
     }
     public void setObj(Object obj) {
         this.obj = obj;
     }
     public Node getNext() {
         return next;
     }
     public void setNext(Node next) {
         this.next = next;
     }
 }

运行结果：

4
bbb
bbb