单链表的Java实现 (二)

前言

前面我们对单链表的表头进行数据的插入和删除，其实也就是实现栈的链式存储。然而仅仅对首个结点进行操作太 easy，我们需要的是对任意位置的查询和删除。

目录

• 查询结点
• 删除任意结点

查询结点

以结点中存储的值为查询的索引

 //根据值查询链表
    private List queryByKey(int key) {
        List current = first;

        while (current.data != key) {
            if (current.next == null) {
                return null;
            } else {

                current = current.next;
            }
        }
        return current;
    }

删除任意结点

和查询结点相似，删除节点需要对链表进行遍历。但删除一个结点需要获取当前结点和前一结点，所有需要两个指针。

 // 删除指定的结点
    public void deleteByKey(int key) {
        List current = first;
        List previous = first;

        while (current.getData() != key) {
            if (current.next == null) {
                return;
            } else {
                previous = current;
                current = current.next;
            }
        }
        // 此时找到了
        if (current == first) {
            first = first.next;
        } else {
            System.out.println("删除" + current.getData());
            previous.next = current.next;

        }


    }

详细代码

// 单链表
// author Ethan


import java.util.Scanner;

public class LinkList {
    // 头结点
    public List first;

    public LinkList() {
        first = null;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int key;
        LinkList linkList = new LinkList();
        //插入数据
        linkList.insertFirst(1);
        linkList.insertFirst(3);
        linkList.insertFirst(5);
        linkList.insertFirst(10);
        linkList.insertFirst(23);
        linkList.insertFirst(35);
        //打印
        linkList.displayAll();
        System.out.println("/");
        //删除头结点
        linkList.deleteFirst();
        linkList.displayAll();
        //根据节点中数据删除特定的结点
        key = in.nextInt();

        linkList.deleteByKey(key);
        System.out.println("/");
        linkList.displayAll();
    }

    public boolean isEmpty() {
        if (first == null) {
            return true;
        } else
            return false;
    }


    //头部插入节点

    public void insertFirst(int data) {
        List listNode = new List(data);

        listNode.next = first;
        first = listNode;

    }


    //删除节点

    public void deleteFirst() {
        first = first.next;

    }

    // 删除指定的结点
    public void deleteByKey(int key) {
        List current = first;
        List previous = first;

        while (current.getData() != key) {
            if (current.next == null) {
                return;
            } else {
                previous = current;
                current = current.next;
            }
        }
        // 此时找到了
        if (current == first) {
            first = first.next;
        } else {
            System.out.println("删除" + current.getData());
            previous.next = current.next;

        }


    }

    //遍历节点
    public void displayAll() {
        if (isEmpty()) {
            System.out.println("空链表");
        } else {
            for (List node = first; node != null; node = node.next) {
                System.out.println(node.getData());
            }
        }
    }

    //根据值查询链表
    private List queryByKey(int key) {
        List current = first;

        while (current.data != key) {
            if (current.next == null) {
                return null;
            } else {

                current = current.next;
            }
        }
        return current;
    }

    // 链表的节点
    class List {
        private int data;
        private List next;

        public List(int data) {
            this.data = data;

        }

        public int getData() {
            return data;
        }
    }

}