Java實現加減乘除（命令行）

//定義一個運算符（+ - * /)接口，定義不同的運算類分別表示上線這個接口並進行相應的運算
//File:OperationTest.java
import java.util.Scanner;
interface Operation{
    double getResult(double numA,double numB);
}
class Plus implements Operation{
    public double getResult(double numA,double numB){
        return numA+numB;
    }
}
class Minus implements Operation{
    public double getResult(double numA,double numB){
        return numA-numB;
    }
}
class Mult implements Operation{
    public double getResult(double numA,double numB){
        return numA*numB;
    }
}
class Div implements Operation{
    public double getResult(double numA,double numB){
        if(numB==0){
            System.out.println("除數不能爲0!");
            return 0;
        }
        return numA/numB;
    }
}
public class OperationTest{
    public static void main(String[] args){
        Scanner input=new Scanner(System.in);
        System.out.println("請輸入兩個數字：");
        double dataA=input.nextDouble();
        double dataB=input.nextDouble();
        System.out.println("請輸入運算符（+ - * /）：");
        char op=input.next().charAt(0);
        Operation operation=null;
        switch(op){
            case '+':
                operation=new Plus();break;
            case '-':
                operation=new Minus();break;
            case '*':
                operation=new Mult();break;
            case '/':
                operation=new Div();break;
            default:
                System.out.println("輸入錯誤！");
        }
        System.out.println(operation.getResult(dataA,dataB));
    }
}