Check if my int contains an int (try/catch)

[Peter Hammar]

Hi!

Im struggeling a little with a try/catch thing. I want to check so that my int x contains an int (if its something else the program crashes). The x should only contain numbers, otherwise the user should be promted to type in a number.

  

System.out.print("Value of x: ");
			Scanner keyboard = new Scanner(System. in);
			x = keyboard.nextInt();
			try {
				
			}
			catch {
				
			}

 

Is there a way to check this?

Regards
Hristo

[fred rosenberger]

if it is an int, what else COULD it contain? (Note: There is a big difference between an int, an Integer, and a String that may contain something that can be parsed into an integer value)

[Peter Hammar]

Ok, my bad, if I type in a "f" for example, instead of an int, the program crashes.

[Rob Spoor]

Check out the hasNextXXX methods of Scanner. They tell you if the next token is an int / byte / ... Don't forget to consume that token or you will loop forever.

[fred rosenberger]

you can also try using the Integer class' parseInt() method. It takes a String and attempts to convert it to an Integer for you, but it can throw an exception.

[Nehel Patel]

Try following...
convert input to Integer, If it is not int value then it will directly go in catch block...

 	 System.out.print("Value of x: ");  
         Scanner keyboard = new Scanner(System. in);  
         
         try {   
         String str = keyboard.next();  
         int x=  Integer.parseInt(str);         
               
         }  
         catch(Exception e) {  
          System.out.print("Type a Number, Not String");               
         } 

[Campbell Ritchie]

Not convinced. You want what Rob said:

System.out.print("Please enter int number: ");
while (!keyboard.hasNextInt()
{
    keyboard.next();
    System.err.print("That wasn't an int number. Try again: ");
}
i = keyboard.nextInt();

Or something similar.

[Rob Spoor]

And note that call on line 4 - it takes away the non-int token so hasNextInt() will evaluate the next token. It's return value is ignored since you don't need it.