哈希表的增加、遍历、查找

哈希表的增加、遍历、查找

package com.wmq.atguigu.hashtable;

import java.util.Scanner;

/**
 * 哈希表
 */
public class HashTableDemo {
    public static void main(String[] args) {
        HashTab hashTab = new HashTab(7);
        String key = "";
        Scanner scanner = new Scanner(System.in);
        while (true) {
            key = scanner.next();
            switch (key) {
                case "add":
                    System.out.println("输入id:");
                    int id = scanner.nextInt();
                    System.out.println("输入名字：");
                    String name = scanner.next();
                    Emp emp = new Emp(id, name);
                    hashTab.add(emp);
                    break;
                case "list":
                    hashTab.list();
                    break;
                case "find":
                    System.out.println("请输入要查找的id:");
                    id = scanner.nextInt();
                    hashTab.findEmpById(id);
                    break;
                case "exit":
                    scanner.close();
                    System.exit(0);
                default:
                    break;
            }
        }
    }
}

//创建一个HashTab 管理多条链表
class HashTab {
    private EmpLinkedList[] empLinkedListArray;
    private int size;                             //表示有多少条链表

    public HashTab(int size) {
        this.size = size;
        empLinkedListArray = new EmpLinkedList[size];
        //初始化链表的每一个链表
        for (int i = 0; i < size; i++) {
            empLinkedListArray[i] = new EmpLinkedList();
        }
    }

    //添加一个雇员
    public void add(Emp emp) {
        int empLinkedListNo = hashFun(emp.id);
        //将emp添加到对应的链表中
        empLinkedListArray[empLinkedListNo].add(emp);
    }

    //遍历所有的链表
    public void list() {
        for (int i = 0; i < size; i++) {
            empLinkedListArray[i].list(i);
        }
    }

    //根据输入的id查找雇员
    public void findEmpById(int id){
        int empLinkedListNo = hashFun(id);
        Emp emp = empLinkedListArray[empLinkedListNo].findEmpById(id);
        if (emp !=null){
            System.out.printf("找到的雇员id = %d\n",empLinkedListNo+1);
        }else {
            System.out.println("没有找到");
        }
    }

    //编写散列函数，使用一个简单的取模法
    public int hashFun(int id) {
        return id % size;
    }
}

//表示一个雇员
class Emp {
    public int id;
    public String name;
    public Emp next;

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

//编写一个链表
class EmpLinkedList {
    private Emp head;

    public void add(Emp emp) {
        if (head == null) {
            head = emp;
            return;
        }
        Emp curEmp = head;
        while (true) {
            if (curEmp.next == null) {
                break;
            }
            curEmp = curEmp.next;
        }
        //退出时将emp加入链表
        curEmp.next = emp;
    }

    //遍历链表的雇员信息
    public void list(int no) {
        if (head == null) {
            System.out.println("链表" + (no + 1) + "为空");
            return;
        }
        System.out.print("第" + (no + 1) + "条链表信息为");
        Emp curEmp = head;
        while (true) {
            System.out.printf("=> id=%d name=%s\t", curEmp.id, curEmp.name);
            if (curEmp.next == null) {
                break;
            }
            curEmp = curEmp.next;
        }
        System.out.println();
    }

    //根据id查找雇员
    public Emp findEmpById(int id) {
        if (head == null) {
            return null;
        }
        Emp curEmp = head;
        while (true) {
            if (curEmp.id == id) {
                break;
            }
            if(curEmp.next == null){
                curEmp = null;
                break;
            }
            curEmp = curEmp.next;
        }
        return curEmp;
    }
}