用Java编写一个计算器

以下是使用Java编写简单的计算器的示例代码：

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter first number: ");
        double num1 = input.nextDouble();
        System.out.print("Enter second number: ");
        double num2 = input.nextDouble();
        System.out.print("Enter operator (+, -, *, /): ");
        char operator = input.next().charAt(0);
        
        double result = 0.0;
        switch (operator) {
            case '+':
                result = num1 + num2;
                break;
            case '-':
                result = num1 - num2;
                break;
            case '*':
                result = num1 * num2;
                break;
            case '/':
                result = num1 / num2;
                break;
            default:
                System.out.println("Invalid operator!");
                return;
        }
        System.out.println(num1 + " " + operator + " " + num2 + " = " + result);
    }
}

该程序使用Scanner类接受用户输入的两个数字和运算符，并使用switch语句计算结果。最后，结果将被打印到控制台上。