Java：雙向鏈表反轉實現

有個小需求要求實現一個雙向鏈表的反轉於是就有了下邊代碼：

鏈表元素結構定義：

package com.util;

public class LinkedNode<T>{
    private T value;
    private LinkedNode<T> prev;
    private LinkedNode<T> next;    
    
    public LinkedNode(T value, LinkedNode<T> prev, LinkedNode<T> next) {
        super();
        this.value = value;
        this.prev = prev;
        this.next = next;
    }

    public T getValue() {
        return value;
    }
    public void setValue(T value) {
        this.value = value;
    }
    public LinkedNode<T> getPrev() {
        return prev;
    }

    public void setPrev(LinkedNode<T> prev) {
        this.prev = prev;
    }

    public LinkedNode<T> getNext() {
        return next;
    }
    public void setNext(LinkedNode<T> next) {
        this.next = next;
    }    
}

鏈表定義:

package com.util;

public class LinkedList<T>{
    private transient int size=0;
    private transient LinkedNode<T> first=null;
    private transient LinkedNode<T> last=null;
    
    /**
     * 添加元素到雙向鏈表頭部
     * */
    public void addFirst(T t){
        LinkedNode<T> oldFirst = first;
        LinkedNode<T> newNode = new LinkedNode<T>(t,  null,oldFirst);
        first = newNode;
      
        if (oldFirst == null)
            last = newNode;
        else
            oldFirst.setPrev(newNode);
        
        size++;
    }
    
    /**
     * 將雙向鏈表轉化為一元數組：從頭開始循環到尾部。
     * */
     public Object[] toArray() {
        Object[] result = new Object[size];
        int i = 0;
        for (LinkedNode<T> node = first; node != null; node = node.getNext())
            result[i++] = node.getValue();
        return result;
    }    
     
     /**
      * 反轉
      * */
     public void reverse(){
         if(first==null||last==null)
             return;
                  
         LinkedNode<T> prev;
         LinkedNode<T> next;
         LinkedNode<T> newFirst=null;
         LinkedNode<T> newLast=null;
         for (LinkedNode<T> node = first; node != null; node = node.getPrev()){
            prev= node.getPrev();
            next= node.getNext();

            if(node.getPrev()==null){
                newLast=node;
            }else if(node.getNext()==null){
                newFirst=node;
            } 
            
            node.setNext(prev);
            node.setPrev(next);                       
         }
         
         first=newFirst;
         last=newLast;
     }
}

備注：這里主要實現了三個功能，在鏈表頭部添加元素、toArray函數、反轉函數，實際上鏈表應該包含其他功能：末尾添加元素，插入元素，索引，移除，遍歷等。

測試代碼：

import com.util.LinkedList;

public class LinkedListTest {
    public static void main(String[] args) {
        LinkedList<String> list=new LinkedList<String>();
        list.addFirst("5");
        list.addFirst("3");
        list.addFirst("1");
        
        for (Object string : list.toArray()) {
            System.out.println(string);
        }
        
        System.out.println("-------------------------------開始反轉-------------------------------");
        list.reverse();
        System.out.println("-------------------------------結束反轉-------------------------------");
        
        for (Object string : list.toArray()) {
            System.out.println(string);
        }        
    }

}