Using Exceptions to validate inputs

[Sumukh Deshpande]

Hello,

I am trying to check whether the value passed by an user is valid constant or not. Here is the code I have written.

enum Media_Delivery {
    Streaming, Progressive
}

public class TestMain {
    public static void main(String[] args) {
        String medi_delivery = "streaming";
        try {
            Media_Delivery.valueOf("streaming");
        } catch (IllegalArgumentException e) {
            System.out.print(e);
        }

    }

}

Now, in above code if the String passed is not withing the listed enum then it throws IllegalArgumentException which is obvious.

But my question is : Is this the proper way to validate? As we are using Java's exception mechanism to validate.

Can someone suggest a better idea or what I have coded above itself is the best option ?

Thanks.

[bhanu chowdary]

I guess its fine. But instead of printing the stack trace it would be good if you display a message, something like "the given input <some input> is not a valid one. The valid values are Streaming, Progessive"

[Campbell Ritchie]

The idea of throwing the Exception is to inform the calling method that there has been an error. Why not put that method invocation into a loop, so you can request new input if the Exception is caught.

boolean needEntry = true
while (needEntry)
{
   try
   {
      ...
      needEntry = false;
   }
   catch ( ... )
   {
      ...
   }
}