Question

I have a number of custom Exception-inheriting classes in my package, which do not differ from their base class. The only purpose I have them is to distinguish one exception cause from the other, when it is thrown. This is how one of my Exception class looks like:

package com.XXX;
/**
 * Thrown when query format is invalid.
 */
public class InvalidFormatException extends Exception {
  /**
   * Public ctor.
   * @param m Supplementary message
   */
  public InvalidFormatException(final String m) {
    super(m);
  }
}

The problem is that all classes are absolutely identical, like twins. The only thing which is different is their names. I don’t like this situation, since it’s an obvious code duplication. In other languages (like PHP, Python, etc.) I would declare these classes on-fly during runtime, but Java doesn’t allow this, as well as I understand. Is there any workaround?

Answer 1

You may create a generic class with a code property settable with the controller. This way you can have only one class and instance when thrown.

That said, I don’t agree when you say classes are twins. They represent totally different functional exception. Based on the separation of concerns pattern, the current implementation is the correct one. Using my generic class will mix concerns in your class and that should be forbidden.

Moreover, I see you inherit from Exception… I will not explains a lot but you should use RuntimeException for functional exceptions in your application. Look around on the web, there is a lot of literature about it.