In the mod I'm working on, I want to have several items which have the same function (searching for entities and making noise when they are found) but with different parameters (search radius, which entity to look for, what noise to make, etc.). In Forge, what is the best way to handle this? My first attempt simply involved copying the code over to each item, but the hassle of changing all of them every time I want to edit the code has grown enough that I'm looking for a more complicated way of approaching the problem.

Should I make a 'SeekerGeneric' class containing all the relevant code and then have various specific items extend that class, each with different parameters? Or is there another way to do things?

Sounds good. Jury-rigged constructor nonsense it is.