Hi,

The why seems obvious to me, nextDouble() sees a non number so throws an
exception and stays where it is. When the while reenters it sees the same
non-number and throws again the exception etc.

The fix I do not know, never having used the Scanner class.

You have to somehow make it all start again on the next input.

claudio

this does not make any sense. Why bother with the loop? The first time
through you exit the method.

Hi,

Have a look at this code:

public class TryNumberParse {
   public static void main( String[] args ) {
       double num = 0.0;

       while( true ) {
           try {
               System.out.print( "Enter a value: " );
               System.out.println( "The value entered was: " + ( num =
getNum() ) );
           } catch( Exception e ) {
               System.out.println( "Invalid value, please re-enter...
" );
               continue;
           }
       }
   }

   private static double getNum() {
       Scanner inp = new Scanner( System.in );
       return inp.nextDouble();
   }
}

Hope it helps!

imanhp@gmail.com wrote in news:1139180450.334075.96290
@g44g2000cwa.googlegroups.com:

A loop with an always-true condition is usually a *very* bad idea.  Only
experienced programmers should ever do this, and only with a very good
reason.

You should also try to avoid using exceptions for common problems, such
as this input problem.  The Scanner class provides methods to avoid
exactly this.

Here is some improved code, with a lot of comments to help you
understand why it is better:

Scanner inp = new Scanner( System.in );
// ask for the first value
System.out.print("enter value: ");
// as long as the user doesn't enter a double
// this is much more intuitive than "as long
// as true is true", as the original code said
while(!inp.hasNextDouble())
{
  // ask to re-enter the value
  System.out.print("re-enter value: ");
  // skip the incorrect value
  inp.next();
}
// inp.hasNextDouble returned true, so we are
// sure that there is a double value in the
// Scanner - no need for exceptions
Double d = inp.nextDouble();
System.out.println("value entered: " + d);