电话号码管理及查询程序Java代码

以下是一个简单的电话号码管理及查询程序Java代码，供参考：

import java.util.HashMap;
import java.util.Scanner;

public class Phonebook {
    private HashMap<String, String> phonebook;

    public Phonebook() {
        phonebook = new HashMap<>();
    }

    public void addEntry(String name, String phone) {
        phonebook.put(name, phone);
    }

    public void removeEntry(String name) {
        phonebook.remove(name);
    }

    public String lookupNumber(String name) {
        return phonebook.get(name);
    }

    public static void main(String[] args) {
        Phonebook phonebook = new Phonebook();
        Scanner scanner = new Scanner(System.in);

        while (true) {
            System.out.println("1. Add entry\n2. Remove entry\n3. Lookup number\n4. Exit");
            int choice = scanner.nextInt();
            scanner.nextLine(); // consume newline

            switch (choice) {
                case 1:
                    System.out.print("Enter name: ");
                    String name = scanner.nextLine();
                    System.out.print("Enter phone number: ");
                    String phone = scanner.nextLine();
                    phonebook.addEntry(name, phone);
                    System.out.println("Entry added.");
                    break;
                case 2:
                    System.out.print("Enter name: ");
                    name = scanner.nextLine();
                    phonebook.removeEntry(name);
                    System.out.println("Entry removed.");
                    break;
                case 3:
                    System.out.print("Enter name: ");
                    name = scanner.nextLine();
                    phone = phonebook.lookupNumber(name);
                    if (phone != null) {
                        System.out.println("Phone number: " + phone);
                    } else {
                        System.out.println("Entry not found.");
                    }
                    break;
                case 4:
                    System.exit(0);
                default:
                    System.out.println("Invalid choice.");
            }
        }
    }
}

该代码使用了HashMap来存储电话号码，提供了添加、删除和查询电话号码的功能。用户可以通过输入数字选择不同的操作，程序会根据用户的选择进行相应的操作。