怎么用Java写出银行存取款的代码

以下是一个简单的Java程序，实现了银行存取款的功能：

import java.util.Scanner;

public class BankAccount {
    private double balance;

    public BankAccount(double initialBalance) {
        balance = initialBalance;
    }

    public void deposit(double amount) {
        balance += amount;
    }

    public void withdraw(double amount) {
        if (balance >= amount) {
            balance -= amount;
        } else {
            System.out.println("余额不足！");
        }
    }

    public double getBalance() {
        return balance;
    }

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

        System.out.print("请输入初始存款金额：");
        double initialBalance = input.nextDouble();

        BankAccount account = new BankAccount(initialBalance);

        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 存款");
            System.out.println("2. 取款");
            System.out.println("3. 查询余额");
            System.out.println("4. 退出");

            int choice = input.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("请输入存款金额：");
                    double depositAmount = input.nextDouble();
                    account.deposit(depositAmount);
                    System.out.println("存款成功！");
                    break;
                case 2:
                    System.out.print("请输入取款金额：");
                    double withdrawAmount = input.nextDouble();
                    account.withdraw(withdrawAmount);
                    System.out.println("取款成功！");
                    break;
                case 3:
                    System.out.println("当前余额为：" + account.getBalance());
                    break;
                case 4:
                    System.out.println("感谢使用本系统！");
                    System.exit(0);
                default:
                    System.out.println("输入错误，请重新选择！");
                    break;
            }
        }
    }
}

在程序中，BankAccount类表示银行账户，包含了存款、取款、查询余额等操作。在main方法中，使用Scanner类获取用户输入的操作选择和金额，然后调用BankAccount类的方法进行相应的操作。程序使用无限循环，直到用户选择退出为止。