利用Java写一个计算器，用户可以自己输入数据，在输入错误信息时提示用户重新输入

以下是一个简单的Java计算器示例代码，它可以让用户输入两个数字和一个操作符，然后计算结果。如果用户输入了无效的数字或操作符，程序将提示用户重新输入。

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double num1, num2, result;
        String operator;

        System.out.print("Enter first number: ");
        while (!input.hasNextDouble()) {
            System.out.print("Invalid input. Please enter a valid number: ");
            input.next();
        }
        num1 = input.nextDouble();

        System.out.print("Enter second number: ");
        while (!input.hasNextDouble()) {
            System.out.print("Invalid input. Please enter a valid number: ");
            input.next();
        }
        num2 = input.nextDouble();

        System.out.print("Enter operator (+, -, *, /): ");
        operator = input.next();
        while (!operator.matches("[+\\-*/]")) {
            System.out.print("Invalid input. Please enter a valid operator (+, -, *, /): ");
            operator = input.next();
        }

        switch (operator) {
            case "+":
                result = num1 + num2;
                break;
            case "-":
                result = num1 - num2;
                break;
            case "*":
                result = num1 * num2;
                break;
            case "/":
                if (num2 == 0) {
                    System.out.println("Division by zero is not allowed.");
                    return;
                }
                result = num1 / num2;
                break;
            default:
                System.out.println("Invalid operator.");
                return;
        }

        System.out.println("Result: " + result);
    }
}

代码中的正则表达式`[+\\-*/]`用于验证操作符是否为+、-、*或/。如果不是，则提示用户重新输入。