title: The "Why" behind PMD's rules
body: <p>Is there a good resource which describes the "why" behind PMD rule sets? <a href="https://pmd.github.io/pmd/" rel="nofollow noreferrer">PMD's site</a> has the "what" - what each rule does - but it doesn't describe why PMD has that rule and why ignoring that rule can get you in trouble in the real world. In particular, I'm interested in knowing why PMD has the AvoidInstantiatingObjectsInLoops and OnlyOneReturn rules (the first seems necessary if you need to create a new object corresponding to each object in a collection, the second seems like it is a necessity in many cases that return a value based on some criteria), but what I'm really after is a link somewhere describing the "why" behind a majority of PMD's rules, since this comes up often enough.</p>
  
  <p>Just to be clear, I know that I can disable these and how to do that, I'm just wondering why they are there in the first place. Sorry if there's something obvious I missed out there, but I did a Google search and SO search before posting this. I also understand that these issues are often a matter of "taste" - what I'm looking for is what the argument for the rules are and what alternatives there are. To give a concrete example, how are you supposed to implement one object corresponding to every object in a loop (which is a common operation in Java) without instantiating each object in a loop?</p>