java - .class错误无法弄清楚

Question

.class 预计在第 68 行返回双结果；该程序无法编译，但我无法弄清楚有人可以帮忙吗？

这是一个基本的计算器 java 文件，它可以输入用户编号并根据输入的运算符对它们执行数学计算

// Calculator.java - This program performs arithmetic, ( +. -, *. /, % ) on two numbers
// Input:  Interactive.
// Output:  Result of arithmetic operation

import javax.swing.*;


public class Calculator
{
    public static void main(String args[]) 
    {
        double numberOne, numberTwo;                
        String numberOneString, numberTwoString;
        String operation;
        double result ;     

        numberOneString = JOptionPane.showInputDialog("Enter the first number: ");
        numberOne = Double.parseDouble(numberOneString); 
        numberTwoString = JOptionPane.showInputDialog("Enter the second number: ");
        numberTwo = Double.parseDouble(numberTwoString); 
        operation = JOptionPane.showInputDialog("Enter an operator (+.-.*,/,%): ");

        // Call performOperation method here        

        result = performoperation(numberOne, numberTwo, operation);
        System.out.format("%.2f",numberOne);
        System.out.print(" " + operation + " ");
        System.out.format("%.2f", numberTwo);
        System.out.print(" = ");
        System.out.format("%.2f", result);

        System.exit(0);

    } // End of main() method.


    // Write performOperation method here.

public static double performOperation(double numberOne, double numberTwo, String operation)

{


double result  = 0;


if (operation .equals("+")){
result = numberOne + numberTwo;
}

else if (operation .equals("-")){
result = numberOne - numberTwo;
}

else if (operation .equals("/")){
result = numberOne / numberTwo;
}

else if (operation .equals("*")){
result = numberOne * numberTwo;
}

else if (operation .equals("%")){
result = numberOne % numberTwo; 
}


return double result; 


System.out.println("The result is " + result);


}// END


} // End of Calculator class.

Answer 1

您的代码中有一些错误:

1. 您试图返回双结果，而实际上，您应该只返回结果。

2. 在您的 main 方法中，您调用了一个不存在的方法，即“performOperation”，而您的方法称为“performOperation”。 Java 区分大小写。

3. 您尝试在返回结果后打印结果，但这是行不通的。您必须在返回之前打印。

我修复了您的一些代码，并将您的 if/else 语句转换为 switch case(我认为当您有重复代码时更容易处理)。

import javax.swing.*;

public class Calculator {

public static void main(String args[]) {
    String numberOneString = JOptionPane.showInputDialog("Enter the first number: ");
    double numberOne = Double.parseDouble(numberOneString);
    String numberTwoString = JOptionPane.showInputDialog("Enter the second number: ");
    double numberTwo = Double.parseDouble(numberTwoString);
    String operation = JOptionPane.showInputDialog("Enter an operator (+.-.*,/,%): ");

    // Call performOperation method here        
    double result = performOperation(numberOne, numberTwo, operation);
    System.out.format("%.2f", numberOne);
    System.out.print(" " + operation + " ");
    System.out.format("%.2f", numberTwo);
    System.out.print(" = ");
    System.out.format("%.2f", result);

    System.exit(0);

} // End of main() method.
// Write performOperation method here.

public static double performOperation(double numberOne, double numberTwo, String operation) {
    double result = 0;

    switch (operation) {
        case "+":
            result = numberOne + numberTwo;
            break;
        case "-":
            result = numberOne - numberTwo;
            break;
        case "/":
            result = numberOne / numberTwo;
            break;
        case "*":
            result = numberOne * numberTwo;
            break;
        case "%":
            result = numberOne % numberTwo;
            break;
        default:
            break;
    }

    System.out.println("The result is " + result);
    return result;

}// END
} // End of Calculator class.