双向链表

简介

它的每个数据结点中都有两个指针，分别指向直接后继和直接前驱。所以，从双向链表中的任意一个结点开始，都可以很方便地访问它的前驱结点和后继结点。

代码

节点对象

class Student2 {
  public int stuNo;
  public String name;
  //指向下一个节点
  public Student2 next;
  //指向上一个节点
  public Student2 prev;

  public Student2() {
  }

  public Student2(int stuNo, String name) {
    this.stuNo = stuNo;
    this.name = name;
  }

  @Override
  public String toString() {
    return "Student2{" +
            "stuNo=" + stuNo +
            ", name='" + name + '\'' +
            '}';
  }
}

不考虑编号排序，直接添加

class DoubleLinkedList {

  //初始化头节点，头节点不能动，不存放具体的数据
  private final Student2  head = new Student2(0,"");

  public Student2 getHead() {
    return head;
  }
/**
   * 不考虑编号顺序，直接添加到最后
   * @param stu 添加的节点对象
   */
  public void add(Student2 stu){
    Student2 temp = head;
    while (temp.next != null) {
      temp = temp.next;
    }
    stu.prev = temp;
    temp.next = stu;
  }

  /**
   * 显示所有节点
   */
  public void show(){
    if(head.next == null){
      return;
    }
    Student2 temp = head.next;
    while (temp != null){
      System.out.println(temp);
      temp = temp.next;
    }
  }
}

 　　Student2 stu1 = new Student2(1,"1号");
    Student2 stu2 = new Student2(2,"2号");
    Student2 stu3 = new Student2(3,"3号");
    Student2 stu4 = new Student2(4,"4号");

    DoubleLinkedList doubleLinkedList = new DoubleLinkedList();
    doubleLinkedList.add(stu1);
    doubleLinkedList.add(stu2);
    doubleLinkedList.add(stu4);
    doubleLinkedList.add(stu3);
　　 doubleLinkedList.show();

按照编号排序添加

/**
   * @param stu 要添加的节点对象
   * 根据编号排序添加
   * 如果要添加的节点已经存在，给出提示
   */
  public void addByNo(Student2 stu){
    Student2 temp = head;
    //标识要添加的学生是否存在
    boolean flag = false;
    while (temp.next != null){
      if(temp.next.stuNo == stu.stuNo){
        flag = true;
        break;
      }
      if(temp.next.stuNo > stu.stuNo){
        break;
      }
      temp = temp.next;
    }
    if(flag){
      System.out.printf("编号为%d的学生已经存在\n",stu.stuNo);
    }else {
      stu.next = temp.next;
      if(temp.next != null){
        temp.next.prev = stu;
      }
      temp.next = stu;
      stu.prev = temp;
    }
  }

　　 doubleLinkedList.addByNo(stu1);
    doubleLinkedList.addByNo(stu2);
    doubleLinkedList.addByNo(stu4);
    doubleLinkedList.addByNo(stu3);
    doubleLinkedList.addByNo(stu3);
    doubleLinkedList.show();

 

 修改

 /**
   *
   * @param stu 要修改的学生对象
   */
  public void update(Student2 stu){
    if(head.next == null){
      System.out.println("链表无数据");
      return;
    }
    boolean flag = false;
    Student2 temp = head;
    while (temp != null){
      if(temp.stuNo == stu.stuNo){
        flag = true;
        break;
      }
      temp = temp.next;
    }
    if(flag){
      temp.name = stu.name;
    }else {
      System.out.printf("编号为%d的学生不存在\n",stu.stuNo);
    }
  }

    doubleLinkedList.addByNo(stu1);
    doubleLinkedList.addByNo(stu2);
    doubleLinkedList.addByNo(stu4);
    doubleLinkedList.addByNo(stu3);
    doubleLinkedList.show();

     Student2 stu = new Student2(4,"00");
    doubleLinkedList.update(stu);
    System.out.println("修改后的数据");
    doubleLinkedList.show();

 

 删除

 /**
   * @param stuNo 根据学生编号删除
   */
  public void delete(int stuNo){
    if(head.next == null){
      System.out.println("链表为空");
      return;
    }
    Student2 temp =head.next;
    //标识要删除的学生是否存在
    boolean flag = false;
    while (temp != null){
      if(temp.stuNo == stuNo){
        flag = true;
        break;
      }
      temp = temp.next;
    }
    if(flag){
      temp.prev.next = temp.next;
      //如果要删除的对象不是最后一个节点
      if(temp.next != null){
        temp.prev = temp.next.prev;
      }
    }else {
      System.out.printf("编号为%d的学生不存在\n",stuNo);
    }
  }

   doubleLinkedList.delete(4);
    doubleLinkedList.delete(1);
    doubleLinkedList.delete(1);
    System.out.println("删除后的数据==============");
    doubleLinkedList.show();