简易计算器Java代码

在Java中编写一个简易计算器的代码，通常会涉及到用户输入两个数字和选择运算符，然后执行相应的计算。下面是一个简单的控制台版计算器的例子：

import java.util.Scanner;

public class SimpleCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("请输入第一个数:");
        double num1 = scanner.nextDouble();
        System.out.println("请输入操作符(+, -, *, /):");
        String operator = scanner.next();

        double num2;
        switch (operator) {
            case "+":
                num2 = scanner.nextDouble();
                double result = add(num1, num2);
                System.out.println("结果: " + result);
                break;
            case "-":
                num2 = scanner.nextDouble();
                result = subtract(num1, num2);
                System.out.println("结果: " + result);
                break;
            case "*":
                num2 = scanner.nextDouble();
                result = multiply(num1, num2);
                System.out.println("结果: " + result);
                break;
            case "/":
                if (num2 != 0) { // 防止除数为零
                    num2 = scanner.nextDouble();
                    result = divide(num1, num2);
                    System.out.println("结果: " + result);
                } else {
                    System.out.println("错误: 除数不能为零!");
                }
                break;
            default:
                System.out.println("错误: 无效的操作符!");
                break;
        }

        scanner.close();
    }

    // 实现加法、减法、乘法和除法的基本方法
    private static double add(double a, double b) {
        return a + b;
    }

    private static double subtract(double a, double b) {
        return a - b;
    }

    private static double multiply(double a, double b) {
        return a * b;
    }

    private static double divide(double a, double b) {
        return a / b;
    }
}

这个程序首先获取用户的输入，然后根据用户指定的运算符调用相应的函数进行计算。记得关闭`Scanner`以释放资源。