java实现hashTable

java实现hashTable

节点类

// 链表的节点
class Node {
    public int id;
    public String name;
    public Node pre;
    public Node next;

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

    public Node(int id, String name) {
        this.id = id;
        this.name = name;
    }

链表类

// 链表
class NodeLinkedList {
    // 头指针
    private Node head;

    // 添加到最后
    public void add(Node node) {
        // 第一次添加
        if (head == null) {
            head = node;
            return;
        }
        Node temp = head;
        while (true) {
            if (temp.next == null) {
                break;
            }
            // 右移
            temp = temp.next;
        }
        temp.next = node;
    }

    // 遍历
    public void show(int id) {
        if (isEmpty()) {
            System.out.printf("第%d条链表为空\n", id);
            return;
        }

        Node temp = head;
        while (true) {
            System.out.println("第" + id + "条链表：" + temp);
            if (temp.next == null) {
                break;
            }
            temp = temp.next;
        }
    }

    // 查找
    public Node getNodeById(int id) {
        if (isEmpty()) {
            return null;
        }

        Node temp = head;
        while (true) {
            if (temp.id == id) {
                return temp;
            }
            if (head.next == null) {
                return null;
            }
            temp = temp.next;
        }
    }

    // 辅助
    private boolean isEmpty() {
        return (this.head == null);
    }
}

哈希表类

// 哈希表
class HashTable {
    private NodeLinkedList[] nodeLinkedLists;
    private int size;

    public HashTable(int size) {
        this.size = size;
        this.nodeLinkedLists = new NodeLinkedList[size];
        // 分别初始化每一个链表
        for (int i = 0; i < size; i++) {
            nodeLinkedLists[i] = new NodeLinkedList();
        }
    }

    // 添加
    public void add(Node node) {
        // 根据id得到员工应该添加的链表
        int hash = hash(node.id);
        // 添加到链表中
        this.nodeLinkedLists[hash].add(node);
    }

    // 遍历
    public void show() {
        for (int i = 0; i < nodeLinkedLists.length; i++) {
            System.out.printf("第%d条链表\n", i);
            nodeLinkedLists[i].show(i);
            System.out.println("==============");
        }
    }

    // 查找
    public Node getNodeById(int id) {
        int hash = hash(id);
        Node node = nodeLinkedLists[hash].getNodeById(id);
        return node;
    }

    // 散列函数,取模法
    private int hash(int id) {
        return id % this.size;
    }
}

测试类

public class Demo {
    public static void main(String[] args) {
        HashTable hashTable = new HashTable(7);

        String key = "";
        Scanner scanner = new Scanner(System.in);

        while (true) {

            System.out.println("add ：添加节点");
            System.out.println("show：展示哈希表");
            System.out.println("search：根据id查找");
            System.out.println("exit：退出");

            key = scanner.nextLine();

            switch (key) {
                case "add":
                    System.out.println("输入id");
                    int id = Integer.parseInt(scanner.nextLine());
                    System.out.println("输入姓名");
                    String name = scanner.nextLine();

                    Node node = new Node(id, name);

                    hashTable.add(node);
                    break;
                case "show":
                    hashTable.show();
                    break;
                case "search":
                    System.out.println("输入id：");
                    id = Integer.parseInt(scanner.nextLine());
                    Node byId = hashTable.getNodeById(id);
                    System.out.println(byId);
                    break;
                case "exit":
                    scanner.close();
                    System.exit(0);
                    break;
                default:
                    System.out.println("输入错了");
                    break;
            }
        }
    }
}