I don't know why FindBugs exactly gives you that first error message. But on the FindBugs website you can look it up in the list of
bug descriptions, where you'll find more info on what the message means exactly and how you could solve it.
For the second point: Whenever you override equals(),
you should override hashCode() as well. These two methods are used together by hash-based collections such as HashMap and HashSet. If they are not implemented according to the rules described in the API documentation for Object.hashCode, then your class will not work properly when used as a HashMap key or value in a HashSet.
See also item 9 in
Effective Java.