Where is the error here?

Programming
1

code here:

class CalculatorConundrum {

public String calculate(int operand1, int operand2, String operation) {

    try {
        if (operation == null) {

            throw new IllegalArgumentException("Operation cannot be null");
        }

        if (operation.isEmpty()) {

            throw new IllegalArgumentException("Operation cannot be empty");
        }
       
        String result;
        switch (operation) {
            case "+":
                result = operand1 + " + " + operand2 + " = " + (operand1 + operand2);
                break;
            case "*":
                result = operand1 + " * " + operand2 + " = " + (operand1 * operand2);
                break;
            case "/":
                if (operand2 == 0) {
                    throw new IllegalOperationException("Division by zero is not allowed");
                }
                result = operand1 + " / " + operand2 + " = " + (operand1 / operand2);
                break;
            default:
                throw new IllegalOperationException("Operation '" + operation + "' does not exist");
        }
        return result;
    } catch (IllegalOperationException e) {
        return "Error: " + e.getMessage();
    } catch (IllegalArgumentException a) {
        return "Error: " + a.getMessage();
    }
}

}

this is my code for the “Java / Calculator Conundrum” exercise, I don’t understand what’s the problem and why it’s wrong, thanks :-)`

2

@Lukerrone It would be helpful if you

  • Add codeblock markers around your code (the </> icon on the editor)
  • Provide the error you get from the test run (in a codeblock, too, not as an image)

Thanks!

1 Like
3 
class CalculatorConundrum {
    public String calculate(int operand1, int operand2, String operation) {
        try {
            if (operation == null) {
                throw new IllegalArgumentException("Operation cannot be null");
            }
            if (operation.isEmpty()) {
                throw new IllegalArgumentException("Operation cannot be empty");
            }
            
            String result;
            switch (operation) {
                case "+":
                    result = operand1 + " + " + operand2 + " = " + (operand1 + operand2);
                    break;
                case "*":
                    result = operand1 + " * " + operand2 + " = " + (operand1 * operand2);
                    break;
                case "/":
                    if (operand2 == 0) {
                        throw new IllegalOperationException("Division by zero is not allowed");
                    }
                    result = operand1 + " / " + operand2 + " = " + (operand1 / operand2);
                    break;
                default:
                    throw new IllegalOperationException("Operation '" + operation + "' does not exist");
            }
            return result;
        } catch (IllegalOperationException e) {
            return "Error: " + e.getMessage();
        } catch (IllegalArgumentException a) {
            return "Error: " + a.getMessage();
        }
    }
}

Handle illegal operation

@Test
@Tag("task:2")
@DisplayName("The calculate method throws IllegalOperationException when passing invalid operation")
public void throwExceptionForUnknownOperation() {
    String invalidOperation = "**";
    String expectedMessage = "Operation '" + invalidOperation + "' does not exist";
    assertThatExceptionOfType(IllegalOperationException.class).isThrownBy(() -> new CalculatorConundrum().calculate(3, 78, invalidOperation)).withMessage(expectedMessage);
}

Test failure

Message: 
Expecting code to raise a throwable.
Exception: java.lang.AssertionError: 
Expecting code to raise a throwable.
	at CalculatorConundrumTest.throwExceptionForUnknownOperation(CalculatorConundrumTest.java:58)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
4

@Lukerrone The test failure message says

Expecting code to raise a throwable

This means, the exception thrown should reach the test, and not be handled in your code. Does that help you?

1 Like
5

ah ok ok now I understand, thanks