Interfaces define a contract between the classes implementing the interfaces and their clients. They are used as an abstraction mechanism so that clients can manipulate "stuff having a given behaviour".
So the general answer to the question "should I create and use this interface?" is: Yes, if you can associate a (a single one) concept being semantically relevant for your clients.
For instance, Comparable is a good interface, because it explains that things can be compared thanks to one of their methods, and as a client I'm interested in dealing with comparable objects (e.g. for sorting them). A contrario, CoolStuff is not a good interface if you admit the cool objects don't have a specific behaviour (in fact, you can imagine a software in which dealing with cool objects makes sense, because they have a common behaviour such as a beCool method).
In your particular case, I believe your interface is useless. Who will use it, how and when? You cannot create an interface for each of the mutable values. So ask yourself what is the relevant and interesting property behind your methods.
If what you want is dealing with objects having all their mutable values accessible through a couple of methods, have a look at the notion of Java bean and the way you can force your classes to adopt their conventions.