java 设计一个简易计算器，能够实现加、减、乘、除、取余等

下面是一个简单的 Java 计算器实现，支持加、减、乘、除、取余等操作：

import java.util.Scanner;

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

        System.out.println("请输入第一个数：");
        double num1 = input.nextDouble();

        System.out.println("请输入运算符(+、-、*、/、%之一)：");
        String operator = input.next();

        System.out.println("请输入第二个数：");
        double num2 = input.nextDouble();

        switch (operator) {
            case "+":
                System.out.println(num1 + " + " + num2 + " = " + (num1 + num2));
                break;
            case "-":
                System.out.println(num1 + " - " + num2 + " = " + (num1 - num2));
                break;
            case "*":
                System.out.println(num1 + " * " + num2 + " = " + (num1 * num2));
                break;
            case "/":
                if (num2 == 0) {
                    System.out.println("除数不能为0！");
                } else {
                    System.out.println(num1 + " / " + num2 + " = " + (num1 / num2));
                }
                break;
            case "%":
                if (num2 == 0) {
                    System.out.println("除数不能为0！");
                } else {
                    System.out.println(num1 + " % " + num2 + " = " + (num1 % num2));
                }
                break;
            default:
                System.out.println("输入的运算符不合法！");
        }
    }
}

通过运行该程序，可以输入两个数字和运算符，计算出结果并输出到控制台。需注意除数为0的情况。