题解 | #简单计算器#

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        while (scan.hasNextLine()) {
            String str = scan.nextLine();
            String[] strs = str.split("[+\\-*/]");//通过+-*/进行字符的分割
            if (strs.length <
                    2) { //如果没有正确的运算符或者无输入，则字符串无法分隔为两部分
                System.out.println("Invalid operation!");
            } else {//分割成功，即输入格式正确
                double num1 = Double.parseDouble(strs[0]);
                double num2 = Double.parseDouble(strs[1]);
                String operate = str.substring(strs[0].length(), strs[0].length() + 1);
                switch (operate) {
                    case "+":
                        System.out.printf("%.4f+%.4f=%.4f\n", num1, num2, num1 + num2);
                        break;
                    case "-":
                        System.out.printf("%.4f-%.4f=%.4f\n", num1, num2, num1 - num2);
                        break;
                    case "*":
                        System.out.printf("%.4f*%.4f=%.4f\n", num1, num2, num1 * num2);
                        break;
                    case "/":
                        if (num2 != 0.0) {
                            System.out.printf("%.4f/%.4f=%.4f\n", num1, num2, num1 / num2);
                        } else {
                            System.out.println("Wrong!Division by zero!");
                        }
                        break;
                }
            }
        }
    }
}