java - 基于用户输入的结果

Question

我一直在学习枚举和 switch 语句，并且我有以下代码

我不想通过代码运行参数，然后编译它以查看结果，我希望用户将数字输入终端和 +,x,/,- 并在终端中返回结果，我该如何完成这个

public class MathCalculatorTest2_0 {
MathFunctions1_0 mathFunction1;
public MathCalculatorTest2_0 (MathFunctions1_0 mathFunction1) {
    this.mathFunction1 = mathFunction1;
}

public void DoMath(double digit1, double digit2) {
    double mathResult = 0;
    switch (mathFunction1) {
        case MULTIPLY:
            mathResult = digit1*digit2;
            break;  
        case DIVIDE:
            mathResult = digit1/digit2;
            break;
        case ADD:
            mathResult = digit1+digit2;
            break;
        case SUBTRACT:
            mathResult = digit1-digit2;
            break;
        default:
            System.out.println("Incorrect arithmatic character, please insert a correct arithmatic character between the two numbers (x, /, +, -)");
    }
    System.out.println(mathResult);
}

public static void main(String[] args) {
    if (args.length < 3) {
        System.out.println("Please correct syntax");
    } else {
        double firstDigit = Double.parseDouble(args[0]);
        String userInput1 = args[1];
        double secondDigit = Double.parseDouble(args[2]);
        MathCalculatorTest2_0 C;
        switch (userInput1) {
            case "x":
                C = new MathCalculatorTest2_0(MathFunctions1_0.MULTIPLY);
                C.DoMath(firstDigit, secondDigit);
                break;
            case "/":
                C = new MathCalculatorTest2_0(MathFunctions1_0.DIVIDE);
                C.DoMath(firstDigit, secondDigit);
                break;
            case "+":
                C = new MathCalculatorTest2_0(MathFunctions1_0.ADD);
                C.DoMath(firstDigit, secondDigit);
                break;
            case "-":
                C = new MathCalculatorTest2_0(MathFunctions1_0.SUBTRACT);
                C.DoMath(firstDigit, secondDigit);
                break;
            default: System.out.println("Please insert correct arithmatic character.");
        }
    }
}

}

public enum MathFunctions1_0 {
MULTIPLY, DIVIDE, ADD, SUBTRACT

}

Answer 1

首先，你的代码中有很多不好的东西，这可能不是它应该看起来的最好版本，但无论如何它要好得多。使用 switch 运算符会很好，并且可以为需要执行的操作声明一些静态最终变量。声明其中包含一些数学工具的静态方法和字段的类:

public class MathTool {
    public static final int PLUS_OPERATION = 0;

    public static final int MINUS_OPERATION = 1;

    public static final int MULTIPLY_OPERATION = 2;

    public static final int DIVIDE_OPERATION = 3;

    public static double doMathOperation(double digit1, double digit2, int operation) {
        switch (operation) {
        case PLUS_OPERATION: return digit1 + digit2;
        case MINUS_OPERATION: return digit1 - digit2;
        case MULTIPLY_OPERATION: return digit1 * digit2;
        case DIVIDE_OPERATION: return digit1 / digit2;
        default: return 0;
        }
    }
}

然后你可以像这样调用它的方法:

    public static void main(String[] args) {
        double operationResult = MathTool.doMathOperation(5, 3, MathTool.MULTIPLY_OPERATION);
        System.out.println(operationResult);
    }

在 Java 中，变量名的首字母应该使用小写。

编辑:

对于来自控制台的用户输入，请使用扫描仪，如下所示:

Scanner sc = new Scanner(System.in);
int i = sc.nextInt();