Thread: How to make Java determine if a values is an integer or not.

You could always try this:
int number;
int number2;
Scanner console = new Scanner(System.in);

try
{
number = console.nextInt();
// OR if using JOptionPane
number2 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter an integer.", "Enter an integer.", JOptionPane.PLAIN_MESSAGE));

}

catch(InputMismatchException imeRef)
{
String str = console.next();
System.out.println("Invalid.");
}

// OR if using JOptionPane

catch(NumberFormatException nfeRef)
{
JOptionPane.showMessageDialog(null, "Invalid.");
}

NOTE: the two int numbers are alternate examples. InputMismatch is for console and NumberFormatException is for JOptionPane.
Don't use both numbers. Also, you may need a while loop and a boolean that will be set to true if the Exception is not caught and originally the boolean is false and therefore, as long as it's not an int, it will keep asking.

I know for InputMismatchException, you have to clean out the invalid results, which is what I did with that String thing in the catch block.

I can't recall if you'd need to reset it for NumberFormatException.

You don't provide any code, so the question is a bit out of context. Do you mean you need to check if a String is a valid int? Then you can a) loop over all the chars and check if each one matches 0-9, b) Use Integer.parseInt in a try/catch - if no exception is thrown its valid, if an exception is thrown it is not valid.

c) Use a regular expresion