question: public int showInputDialogForPositiveIntegerInput ( final String message , final String suggestedInput ) { String lineWidth = suggestedInput ; while ( 1 > 0 ) { lineWidth = JOptionPane . showInputDialog ( null , message , lineWidth ) ; if ( lineWidth == null ) { return 0 ; } try { return Integer . parseInt ( lineWidth ) ; } catch ( final NumberFormatException ex ) { JOptionPane . showMessageDialog ( null , "'" + lineWidth + "' is not a valid positive integer value." , "Invalid Input" , JOptionPane . ERROR_MESSAGE ) ; } } }
target:  Forces the user to either enter nothing or a positive integer