RE: JOptionPane Prompt

[bleh]

Hello, I had a quick question for some of you experts out there.

I have an assignment where I have to set up a loop that sets it so that you cannot input a negative number

if (x < 0)
{
JOptionPane.showMessageDialog(null, "Cannot be negative, try again");
JOptionPane.showInputDialog("How tall are you");
}

When I put two negative numbers in a row, it just moves on. However, when I change the if-statement to a while-loop, the executed application never closes, even when I put in a positive number. How can I turn this into something that asks the question more than once, if I keep inputting a negative number?

Thanks

[pbrockway2]

when I change the if-statement to a while-loop, the executed application never closes, even when I put in a positive number.

It is not enough to just ask the question inside the loop: you also have to set the value of x so that the updated value will be checked.

If have problems doing this post the code you are using: just a brief example with a main() method that prompts until it gets a valid response.

[bleh]

I apologize, I do not understand what you are saying. Could you provide an example?

edit: maybe this might help..

String height = JOptionPane.showInputDialog("How tall are you");
int x = Integer.parseInt(height);

while (x < 0)
{
JOptionPane.showMessageDialog(null, "Cannot be negative, try again");
JOptionPane.showInputDialog("How tall are you");
}

[TheEnemy]

As pbrockway2 said, the issue is that your while loop never update height after the user enters it the second time, so it'll loop forever with the negative number entered the first time. This small change should make sure that as soon as you enter a non-negative number, the loop will stop.

String height = JOptionPane.showInputDialog("How tall are you");
int x = Integer.parseInt(height);
    	
while (x < 0)
{
	JOptionPane.showMessageDialog(null, "Cannot be negative, try again");
	height = JOptionPane.showInputDialog("How tall are you");
	x = Integer.parseInt(height);
}

Also note that if you enter something else than a number (letter, special characters, etc.) your parseInt call will throw a NumberFormatException.