Using exception handling to eliminate irrelevant exceptions in subclass constructor

Question

I'm writing a class in Java which is a subclass of another class I wrote, and its constructor explicitly calls the superclass's constructor. The constructor of the superclass may throw several types of exceptions when initialized directly, however when I initialize an instance of my subclass there are several exceptions that will never by thrown (by design).

I tried catching these exceptions in the subclass's constructor but I received an error stating that "Constructor call must be the first statement in a constructor". Why can't I catch these exceptions?

For example, the code below:

public class Persian_Cat extends Cat {

    public Persian_Cat(File file) {
        try{
            super(file);
        } catch(InvalidArgumentException e) {
        } catch(FileNotFoundException e) {
        }
    }
}

marks the statement super(file); as the error.

How can I implement the subclass constructor so that it will know these exceptions are irrelevant? I need this because I don't wish to wrap this constructor in try{}...catch{} for every exception in my code later.

Answer 1

Sadly, if you use super(...); it must be the very first line of code in the constructor. There is no way to avoid this.

One solution would be to create another constructor that doesn't throw those exceptions. It may be sensible to scope this as protected, rather than public. You would want to document the API to make it clear which input validation (or whatever) is not being conducted because of which assumptions.