Confused in Exception Handling Assignment!!

[rugger06]

I have come to a logical impasse with my current exception handling assignment! :confused:

The purpose of the assignment is to use try and catch blocks to implement exception handling logic.

The assignment requirements follow:

1. Create your exception in a file called ScoreException.java. Create the UseScoreException.java class to use this exception. The UseScoreException.java file will have the main() method.

2. Prompt the user to enter a test score. Read this score using a dialog box.

3. Any input value greater than 100 or less than 0 should generate the ScoreException exception. You must throw a ScoreException exception at least once and you must have a catch block that catches a ScoreException exception. Use the getMessage method of the Throwable class to display the message associated with this exception. You may do other processing also if you wish. This catch block must display a dialog box with "The score must be >= 0 and <= 100!".

4. Display a dialog box with "Do you want to enter another score?" after the user clicks the OK button.

5. Use the "parseXXXX" methods to convert the String read from the input dialog. This method will throw a NumberFormatException if it is unable to convert the String object to a valid number. Any input value that has characters other than numbers, a decimal, or a negative sign will generate the NumberFormatException exception. You must have a catch block that catches a NumberFormatException exception. This catch block must display a dialog box with "You must enter a number for the score!".

6. Display a dialog box like #4 above ("Do you want to enter another score?") after the user clicks the OK button.

7. Display a dialog box with "That is a valid score." if a valid score is entered.

8. Display a dialog box like #4 above ("Do you want to enter another score?") after the user clicks the OK button.

9. Continue the steps above until the user clicks the No command button when presented with the dialog box in #4 ("Do you want to enter another score?").

I don't need to worry about the program logic for the Cancel command or the Cancel icon.

Here is the code for my ScoreException class:

public class ScoreException extends Exception
{//begin class
	public ScoreException()//constructs new Exception, takes no arguments
	{
		super("The score must be >= 0 and <= 100!");//Specified detail message
	}
}//end class

Here is the code for my UseScoreException (sorry for all the comments, it helps to keep me organized!)

import javax.swing.*;

class UseScoreException
{//begin class
	
	public static void main(String[] args) throws ScoreException
	{//begin main method
		
	//declaration of class variables
	int score = 0;//declares and initializes variable
	String inputString;//declares String that will accept user input
	final int MAX_SCORE = 100;//declares max limit for scores
	boolean isYes;
	
	try
	{//begin try block	
	do
	{//begin do block of statements
		inputString = JOptionPane.showInputDialog(null, "Enter test score for student.", 
			"Enter Score", JOptionPane.QUESTION_MESSAGE);
	score = Integer.parseInt(inputString);//holds input value String and converts it to int

	if (score > MAX_SCORE || score < 0)//evaluates score input against upper and lower limits
	{//begin "if" block of statements
		throw new ScoreException();
	}//end "if" block of statements
	else
	{//begin "else" block of statements
		JOptionPane.showMessageDialog(null, "That is a valid score.", "Valid Score",
				JOptionPane.INFORMATION_MESSAGE);
	}//end "else" block of statements
	}//end do block of statements
	while
		(score > MAX_SCORE || score < 0);

	}//end try block
	
	catch(ScoreException se)
	{//begin ScoreException block of statements
		JOptionPane.showMessageDialog(null, se.getMessage(), "Score Error",
				JOptionPane.ERROR_MESSAGE);
	}//end ScoreException block of statements
	
	/*try
	{//begin try block
	int selection = JOptionPane.showConfirmDialog(null, "Do you want to enter another score?", 
			"Enter Score", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
	do
		{
		inputString = JOptionPane.showInputDialog(null, "Enter test score for student.", 
				"Enter Score", JOptionPane.QUESTION_MESSAGE);
		score = Integer.parseInt(inputString);//holds input value String and converts it to int
		}
	while
		(score <= MAX_SCORE || score >= 0);
		//(isYes = (selection == JOptionPane.YES_OPTION));	
	}//end try block
	*/
	
	catch(NumberFormatException nfe)
	{//begin NumberFormatException block of statements
		JOptionPane.showMessageDialog(null, "You must enter a number for the score!",
				"Score Error", JOptionPane.ERROR_MESSAGE);
	}//end NumberFormatException block of statements
	
	}//end main method

}//end class

I know I need to write the code (second try block after the catch ScoreException()) that I have within the multiple line comment block into the first try block, but I can't figure out how to do it correctly. That's why it's sitting as a comment for now. The logic on how to write this correctly without using an endless series of if-else statements escapes me! I've been grinding away at this part for over two days straight.

Can anyone help me please?

[snotmare]

Here's some pseudo code, try something along these lines...

score = 0
while score != 0
    try{
        inputString = JOptionPane.showInputDialog(null, "Enter test score for student.", "Enter Score", JOptionPane.QUESTION_MESSAGE);
        int inputScore = Integer.parseInt(inputString);

        if (score > MAX_SCORE || score < 0)
            throw new ScoreException();
        else
            score = inputScore
    }catch(ScoreException e){
         JOptionPane.showMessageDialog(null, "That is a valid score.", "Valid Score", JOptionPane.INFORMATION_MESSAGE);

        //if the user cancels, code a break here;
    }
}

[Fubarable]

Get rid of most of those comments when posting code here because it really makes your code hard to read. I think that you probably don't want this line in your ScoreException constructor:

super("The score must be >= 0 and <= 100!");//Specified detail message

as it adds little. Rather perhaps you want two constructors, one the default constructor and another that takes a String parameter and passes that String to the super constructor.

In your code that uses the exception, perhaps you want to create a method that throws the exception if the input is bad, and then in another method call the first method in a try/catch block that catches this exception.

e.g.,

public class Foo003 {
   
   public static void main(String[] args) {
      //... some code here
      
      try {
         methodThrowsException();
      } catch (ScoreException e) {
         // TODO: handle exception
      }
   }
   
   public static void methodThrowsException() throws ScoreException {
      // get test score,
      // if bad, throw the exception
   }   
}

[Fubarable]

Here's some pseudo code, try something along these lines...

score = 0
while score != 0
    try{
        inputString = JOptionPane.showInputDialog(null, "Enter test score for student.", "Enter Score", JOptionPane.QUESTION_MESSAGE);
        int inputScore = Integer.parseInt(inputString);

        if (score > MAX_SCORE || score < 0)
            throw new ScoreException();
        else
            score = inputScore
    }catch(ScoreException e){
         JOptionPane.showMessageDialog(null, "That is a valid score.", "Valid Score", JOptionPane.INFORMATION_MESSAGE);

        //if the user cancels, code a break here;
    }
}

It seems funny (at least to me) to throw the exception from within that try block. Why not simply us if/else rather than an exception that can't possibly percolate up a stack chain? Maybe it's just me, but it seems much more natural to have a method throw the exception as in my example.

[rugger06]

Thank you both for the help!

Using a while loop with the boolean condition was what worked for me.

[JosAH]

I think that you probably don't want this line in your ScoreException constructor:

super("The score must be >= 0 and <= 100!");//Specified detail message

as it adds little. Rather perhaps you want two constructors, one the default constructor and another that takes a String parameter and passes that String to the super constructor.

I'm not so sure about that; the assignment explicitly states that any number will do as long as it is in the range [0, 100]. Anticipating for a more general situation is fine as long as it is used. The solution to the assignment problem will (most likely) never use another interval.

In general: anticipating for possible future cases causes (a bit of) code bloat and can be added later when needed. I often find myself removing lots of (small) methods that could've been handy but are never used although they could've been useful. I don't know where to draw the line here ... Generalizing can be fun now and then but its use is limited in my experience.

kind regards,

Jos (<--- your free Sunday's philosopher ;-)