Testing user input for integer data type?

[Brandt Charles]

Let me elaborate, I need input to be in integer format. Any other will need to throw an exception. I went poking around in the Integer class to no avail, but is there a method to test if an element of an array of this input is an integer? I expect it could be done through some regex magic, of which I am not proficient, but was hoping there was an easier way.

Thanks in advance,

Brandt
[ August 05, 2006: Message edited by: Brandt Charles ]

[Keith Lynn]

Originally posted by Brandt Charles:
Let me elaborate, I need input to be in integer format. Any other will need to throw an exception. I went poking around in the Integer class to no avail, but is there a method to test if an element of an array of this input is an integer? I expect it could be done through some regex magic, of which I am not proficient, but was hoping there was an easier way.

Thanks in advance,

Brandt

[ August 05, 2006: Message edited by: Brandt Charles ]

I would set up a try/catch and catch a NumberFormatException.

[Garrett Rowe]

In this case "regex magic" is easy

boolean isInteger = inputString.matches("\\d+");

[ August 05, 2006: Message edited by: Garrett Rowe ]

[Amit Batra]

you could convert the primitive to the wrapper equiv and then use the instanceof test.

[Amit Batra]

Sorry I didnt read that you wanted an exception which means your value will be coming in from runtime.

class A{
public static void main(String[] args){
try{
int b=new Integer(Integer.parseInt(args[0]));

}catch(Exception e){
System.out.println("An exception has been thrown");
}
}
}

[Stan James]

regex gets tricky if you want to allow plus and minus signs and enforce data ranges. I find it more expressive to use Integer.parseInt() and catch the exception in a little boolean method that does nothing else.

There is a cost to throwing an exception but it takes batches of thousands or millions to matter. If you do this with interactive user input the user will never notice the overhead.

[Layne Lund]

How does the user input this integer? Are you creating a console interface or a GUI? All the above will work fine if you are using plain text. However, if you are doing a GUI, you might want to look into using JFormattedTextField.

Layne

[Brandt Charles]

Thanks, everyone. But Garrett and Keith are the winners. I integrated both of your solutions, and it worked splendidly. The matches() method could not have been easier to use.

Thanks again!