自定义一个LinkedList

package com.hcy.collection;

/**
 * @author hcy
 * 自定义LinkedList
 */


 class Node{
	Node previous;
	Node next;
	Object element;
	
	public Node(Object element) {
		super();
		this.element = element;
	}
	
}


public class MyLinkedList {
	
	private Node first;
	private Node last;
	
	private int size;
	
	public MyLinkedList() {
	//	super();
		this.first = null;
		this.last = null;
	}
	
	public int size(){
		return size;
	}
	
	public void remove(int index){
		
		Node temp = getNode(index);
		
		if(temp != null){
			Node up = temp.previous;
			Node down = temp.next;
			if(up!=null && down!=null){
				up.next = down;
				down.previous = up;
			}
			if(up==null){
				down.previous = null;
				first = down;
			}
			if(down==null){
				up.next = null;
				last = up;
			}
		}
	}
	
	public Node getNode(int index){
		Node temp = null;

		if (index <= (index >> 2)) {
			temp = first;
			for (int i = 0; i < index; i++) {
				temp = temp.next;
			}
		} else {
			temp = last;
			for (int i = size - 1; i > index; i--) {
				temp = temp.previous;
			}
		}

		return temp!=null?temp:null;
	}
	
	public Object get(int index){
		
		if(index<0||index>size-1){
			throw new RuntimeException("索引不合法："+index);
		}
		
		Node temp = null;	
		temp = getNode(index);
		
		return temp.element;
		
	}
	
	public void add(Object element){
		
		Node node = new Node(element);
		
		if(first == null){			
			first = node;
			last = node;
		}else{
			node.previous = last;
			node.next = null;
			
			last.next = node;
			last = node;
		}
		size++;
	}
	
	@Override
	public String toString() {
		StringBuffer sb = new StringBuffer();
		Node temp = first;
		
		sb.append("[");
		while(temp != null){
			sb.append(temp.element+",");
	//		System.out.println(temp.element);
			temp = temp.next;
			
		}
		sb.setCharAt(sb.length()-1, ']');
		return sb.toString();
	}


	public static void main(String[] args) {
		
		MyLinkedList list = new MyLinkedList();
//		list.add("a");
//		list.add("b");
		for(int i = 0;i<20;i++){
			list.add("a"+i);
			
		}
		
		System.out.println(list);
		System.out.println(list.size());
		System.out.println(list.get(5));
		System.out.println(list.get(13));
		list.remove(7);
		System.out.println(list);
	}

}