[계산기 과제]https://github.com/ethrad/Java_Calculator/tree/main/src/Homework 도전 기능만 작성함. App.java import java.util.Scanner;public class App { public static void main(String[] args) { ArithmeticCalculator calc = new ArithmeticCalculator(); Scanner sc = new Scanner(System.in); Parser parser = new Parser(); while (true) { double firstNumber; // 올바른 수..