Is it bad practice for a class to have only static fields and methods?

I have a class that consists only of static member variables and static methods. Essentially, it is serving as a general-purpose utility class.

Is it bad practice for a class to contain only static member variables and static methods?

No, I don't think so at all. It is worse practice to have a class full of instance methods which don't actually depend on a particular instance. Making them static tells the user exactly how they are intended to be used. Additionally, you avoid unnecessary instantiations this way.

EDIT: As an afterthought, in general I think its nice to avoid using language features "just because", or because you think that that is the "Java way to do it". I recall my first job where I had a class full of static utility methods and one of the senior programmers told me that I wasn't fully harnessing the OO power of Java by making all of my methods "global". She was not on the team 6 months later.

As long as the class has no internal state and is essentially what is known as a leaf class (utility classes fall into this category), in other words it is independent of other classes. It is fine.

The Math class being a prime example.