Java双向链表倒置功能实现过程解析

public void reversed() {
　　if (head == null || head.getRight() == null) {
　　　　return;
　　}
　　current = head;
　　while(true) {
　　　　//交换左右节点
　　　　Node tmp = head.getLeft();
　　　　head.setLeft(head.getRight());
　　　　head.setRight(tmp);

　　　　//如果左节点为空，则终止，否则循环执行
　　　　if (head.getLeft() == null) {
　　　　　　return;
　　　　} else {
　　　　　　head = head.getLeft();
　　　　}
　　}
}

<&＃63;xml version="1.0" encoding="UTF-8"&＃63;>

  4.0.0

  cn.jiashubing
  alitest
  1.0-SNAPSHOT

  
    
      junit
      junit
      4.12
    
  

package cn.jiashubing;

/**
 * 自定义节点
 *
 * @author jiashubing
 * @since 2018/3/30
 */
class Node {

  /**
   * 当前值
   */
  private T data;

  /**
   * 左节点
   */
  private Node left;

  /**
   * 右节点
   */
  private Node right;

  Node(T data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }

  T getData() {
    return data;
  }

  void setData(T data) {
    this.data = data;
  }

  Node getLeft() {
    return left;
  }

  void setLeft(Node left) {
    this.left = left;
  }

  Node getRight() {
    return right;
  }

  void setRight(Node right) {
    this.right = right;
  }
}

package cn.jiashubing;

/**
 * 自定义双向链表
 *
 * @author jiashubing
 * @since 2018/3/30
 */
public class MyLinkedList {
  /**
   * 头结点
   */
  private Node head;

  /**
   * 当前节点
   */
  private Node current;

  /**
   * 添加节点
   * 如果头节点为空，则赋值为当前节点
   * 否则，要双向设置，当前节点向后移动一位
   *
   * @param data 当前节点的值
   */
  public void add(T data) {
    if (head == null) {
      head = new Node(data);
      current = head;
    } else {
      Node tmp = new Node(data);
      current.setRight(tmp);
      tmp.setLeft(current);
      current = current.getRight();
    }
  }

  /**
   * 正向打印链表
   *
   * @param node 当前节点
   */
  public void print(Node node) {
    if (node == null) {
      return;
    }

    Node tmp = node;
    while (tmp != null) {
      System.out.print(tmp.getData() + " ");
      tmp = tmp.getRight();
    }
    System.out.println("");
  }


  /**
   * 反向打印链表
   *
   * @param node 当前节点
   */
  public void printRev(Node node) {
    if (node == null) {
      return;
    }

    Node tmp = node;
    while (tmp != null) {
      System.out.print(tmp.getData() + " ");
      tmp = tmp.getLeft();
    }
    System.out.println("");
  }


  /**
   * 链表倒置
   */
  public void reversed() {
    if (head == null || head.getRight() == null) {
      return;
    }
    current = head;
    while(true) {
      //交换左右节点
      Node tmp = head.getLeft();
      head.setLeft(head.getRight());
      head.setRight(tmp);

      //如果左节点为空，则终止，否则循环执行
      if (head.getLeft() == null) {
        return;
      } else {
        head = head.getLeft();
      }
    }
  }

  public Node getHead() {
    return head;
  }

  public Node getCurrent() {
    return current;
  }

}

import cn.jiashubing.MyLinkedList;
import org.junit.Before;
import org.junit.Test;

/**
 * @author jiashubing
 * @since 2018/3/30
 */
public class JunitTest {

  private MyLinkedList list;

  @Before
  public void setNum() {
    list = new MyLinkedList();
    for (int i = 1; i <4; i++) {
      list.add(i);
    }
    System.out.println("正向打印: ");
    list.print(list.getHead());
  }

  @Test
  public void test1() {
    System.out.println("链表倒置后正向打印 ");
    list.reversed();
    list.print(list.getHead());
  }

  @Test
  public void test2() {
    System.out.println("逆向打印 ");
    list.printRev(list.getCurrent());
  }
}