Java数据结构之双向链表的实现

public class StudentNode {
    public String no; //学号
    public String name; //姓名
    public int age; //年龄
    public StudentNode pre; //指向前一个节点
    public StudentNode next; //指向下一个节点

    //构造器
    public StudentNode(String no, String name, int age ){
        this.no = no;
        this.name = name;
        this.age = age;
    }

    //为了显示方便
    @Override
    public String toString() {
        return "StudentNode{" +
                "no='" + no + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

public class StudentDoubleLinkedList {
    //定义头节点
    private StudentNode head = new StudentNode("", "", 0);

    //获取头节点
    public StudentNode getHead(){
        return head;
    }

    //遍历双向链表的方法
    public void showList(){
        //判断链表是否为空
        if (head.next == null){
            System.out.println("当前链表为空");
            return;
        }
        //遍历 使用辅助指针
        StudentNode temp = head;
        while (temp != null){
            //更新指针
            temp = temp.next;
            if (temp.next == null){
                System.out.print(temp);
                break;
            }
            System.out.print(temp + "--->");
        }
    }

    //添加节点的方法
    //添加到尾部
    public void add(StudentNode newNode){
        //先找到最后一个节点
        StudentNode cur = head;
        while (true){
            //到达最后退出循环
            if (cur.next == null){
                break;
            }
            //更新指针
            cur = cur.next;
        }
        //添加操作
        newNode.next = cur.next; //也可以省略，因为恒为null
        cur.next = newNode;
        newNode.pre = cur;
    }

    //添加节点的方法
    //根据学号顺序添加
    public void addByOrder(StudentNode newNode){
        //如果当前链表为空，则直接添加
        if (head.next == null){
            head.next = newNode;
            newNode.pre = head;
            return;
        }
        //按照学号找到对应位置
        StudentNode cur = head;
        boolean flag = false; //标识待添加的no是否存在
        while (true){
            if (cur.next == null){
                //已经到达链表的尾部
                break;
            } else if (Integer.parseInt(cur.next.no) == Integer.parseInt(newNode.no)){
                //已经存在
                flag = true;
                break;
            }else if (Integer.parseInt(cur.next.no) > Integer.parseInt(newNode.no)){
                //位置找到
                break;
            }
            cur = cur.next;
        }
        if (flag){
            System.out.println("当前no已经存在，无法添加!");
        }else {
            //添加操作
            newNode.next = cur.next;
            cur.next = newNode;
            newNode.pre = cur;
        }
    }

    //根据no学号修改学生信息
    public void update(StudentNode studentNode){
        if (head.next == null){
            System.out.println("当前链表为空, 无法修改");
            return;
        }
        StudentNode temp = head.next;
        boolean flag = false; //表示是否找到节点
        while (true){
            if (temp == null){
                break;
            }
            if (temp.no == studentNode.no){
                flag = true;
                break;
            }
            temp = temp.next;
        }
        if (flag){
            temp.name = studentNode.name;
            temp.age = studentNode.age;
            System.out.println("更新成功!");
        }else {
            System.out.println("没有找到");
        }
    }

    //从双向链表中删除节点
    public void delete(String no){
        //直接找到对应no的节点直接删除
        StudentNode cur = head.next;
        boolean flag = false; //标记是否找到
        while (true){
            if (cur == null){
                break;
            }
            if (cur.no.equals(no)){
                flag = true; //找到了
                break;
            }
            cur = cur.next;
        }
        if (flag){
            //删除操作
            //注意考虑最后一个节点后一个为空的情况
            if (cur.next != null) {
                cur.next.pre = cur.pre;
            }
            cur.pre.next = cur.next;
            System.out.println("删除成功!");
        }else {
            System.out.println( no + "节点不存在，无法删除！");
        }
    }
}

public class DoubleLinkedListDemo {
    public static void main(String[] args) {
        StudentDoubleLinkedList doubleLinkedList = new StudentDoubleLinkedList();
        doubleLinkedList.addByOrder(new StudentNode("1", "黄小黄", 20));
        doubleLinkedList.addByOrder(new StudentNode("3", "懒羊羊", 20));
        doubleLinkedList.addByOrder(new StudentNode("2", "沸羊羊", 25));
        doubleLinkedList.addByOrder(new StudentNode("4", "美羊羊", 15));
        System.out.println("遍历:");
        doubleLinkedList.showList();

        //测试更新方法
        System.out.println("\n更新编号为4的信息后:");
        doubleLinkedList.update(new StudentNode("4", "祢豆子", 14));
        doubleLinkedList.showList();

        //测试删除方法
        System.out.println("\n删除第一个和最后一个:");
        doubleLinkedList.delete("1");
        doubleLinkedList.delete("4");
        doubleLinkedList.showList();
    }
}