This is an inheritance from C where only a single primitive value could be returned. In java you Can also return a single object.
So for new code return an object of a basetype with the subtype indicating the problem to be used with instaceof, or throw a "not Found" exception.
For existing special values make -1 a constant in your code names accordingly - NOT_FOUND - so the reader Can tell the meaning without having to check javadocs.
