我怎样才能用一种方法来制作这个计算器呢？

Question

我试着做这个计算器，我可以用四种方法，一种是加法，一种是减法，还有.....但我想让它变得尽可能简单。我如何使用一个方法执行4个主要操作，然后在静态main中调用它？

package com.company;

import java.util.Scanner;

public class Main {
    final static String first = "first number: ";
    final static String sec = "second number: ";

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("what do you want to use? (multiply (input *), divide (input /), subtract (input -), addition (input +)");
        String input = scanner.nextLine();
        double answer = calculation(input);                 ----------------------
        System.out.println(answer);
    }
    public static double calculation(double element){       ----------------------
        Scanner scanner = new Scanner(System.in);
        System.out.println(first);
        double firstInput = scanner.nextDouble();
        System.out.println(sec);
        double secInput = scanner.nextDouble();
        return firstInput element secInput;                 ----------------------
    }
}

可以将元素更改为(+-*/)吗？（那部分是我有问题）

Answer 1

您可能想看看OOP原则，使用继承和多态性，您应该能够在接口中定义一个方法，并且在您的类中实现它，这样您就可以有一个带有execute方法的计算接口，然后用Sum类实现该接口，其中execute方法执行真正的Sum。

public interface Calculation {
    Double execute(Double a, Double b);
}

public class Sum implements Calculation {
    @Override
    public Double execute(Double a, Double b) {
        return a+b;
    }
}

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("what do you want to use? (multiply => *, divide => /, subtract => -, addition => +");
        String input = scanner.nextLine();
        Calculation calculation;
        if (input.equals("+")) calculation = new Sum();
        else calculation = new Sum();// Just initializing calculation to avoid compilation error
        double answer = execute(calculation);
    }

    private static double execute(Calculation calculation){
        Scanner scanner = new Scanner(System.in);
        double firstInput = scanner.nextDouble();
        System.out.println(firstInput);
        double secInput = scanner.nextDouble();
        System.out.println(secInput);
        return calculation.execute(firstInput, secInput);
    }
}