Can I cache getClass.hashCode()?

Whatever the reason, I have the following hashCode implemented in my abstract class.

@MappedSuperclass
abstract Some {

    @Override
    public boolean equals(final Object obj) {
        // ...
    }

    @Override
    public int hashCode() {
        return getClass().hashCode(); // TODO: cache, maybe?
    }
}

1. Can I cache the value of the getClass().hashCode()?
2. Is there any possibility of the value being changed while running in a JVM?
3. Is this some kind of the premature optimization shit?

1. Can I cache the value of the getClass().hashCode()?

You can, but ...

2. Is there any possibility of the value being changed while running in a JVM?

No possibility. The class of a Java object cannot change, and the hashcode of a Java Class object (which is the result type for getClass()) cannot change.

3. Is this premature optimization?

Probably yes¹.

However, using the hashcode of the object's class as the hashcode of an object is a very bad idea from a performance perspective.

Doing that means that all instances of the class (e.g. Some) will have the same hashcode². That will lead to a bazillion hash collisions, and make most HashSet and HashMap operations O(N) or O(logN) (depending on your Java version) rather than O(1).

^{1 - I am assuming you have not done a bunch of performance analysis that you haven't told us about. If you had already done the analysis, then maybe this is not a premature optimization.
2 - I am assuming that the Some::hashCode method is not overridden to something more sensible by concrete subclasses of Some.}