Some questions about Collections

Question

getItem(index or name): when to throw an exception when to return null?
getIndex(Item): when to return -1 when exception?
Is it better to have two versions of a method?

Answer 1

What if I pass in -1 as the index?
What if there are 10 items and I pass in 100,000?jschell,
The choice to throw an exception or to return null is
dependent on the application. If the container so
feels that -1 or 10,000 shall impair its functionality
or has impaired its functionality and it cannot
recover from it - by all means, go ahead and throw
your exception.Certainly. But the question wasn't addressing a specific application but rather a single component.
Given that my presumption would be to write the component based on the standpoint of a library and not an application.
That means that the component must make a decision based on correctness for the component, which is obvious since it can't do it based on correctness of the application.
This would suggest that if a index is passed in that exceeds the boundaries of the collection that throwing an exception is the correct decision. Because it exceeds the correctness of the average collection. Naturally that might not be true for a specific kind of collection, but the question wasn't addressing a specific kind of collection.
>
Vector is just an instance of a type of container - no
body stops you from creating your own container and
also in Vector - please notice that both are
RuntimeException.
Yes Vector uses a unchecked exception for boundary problems. Which one could take to suggest that in the general case that is a good idea.
In the ultimate equation, it is the form that you
chose that shall dictate wether you return null or
throw an Exception. There is nothing absolute in this
matter. My point was more subtle (to point to you, if
you have failed to notice) - "Do not throw Excception,
until you are sure that you cannot recover from the
problem and proceed correctly".I agree there are no absolutes. But I also think that when boundary conditions are exceeded in libraries then exceptions should be used most of the time. I believe most third party libraries take this stance. As an alternative sometimes they also provide a checked and unchecked versions which allows the user to decide the best recourse.