In Java, is there any disadvantage to static methods on a class?

Question

Lets assume that a rule (or rule of thumb, anyway), has been imposed in my coding environment that any method on a class that doesn\'t use, modify, or otherwise need any ins

Answer 1

I really like this question as this has been a point I have been debating for last 4 years in my professional life. Static method make a lot of sense for classes which are not carrying any state. But lately I have been revised my though somewhat.

Utility classes having static methods is a good idea.

Service classes carrying business logic can be stateless in many cases. Initially I always added static methods in them, but then when I gained more familiarity with Spring framework (and some more general reading), I realized these methods become untestable as an independent unit as u cannot inject mock services easily into this class. E.g. A static method calling another static method in another class, there is no way JUnit test can short circuit tis path by injecting a dummy implementation at run time.

So I kind of settled to the thought that having utility static methods which do not need to call other classes or methods pretty much can be static. But service classes in general should be non static. This allows you to leverage OOPs features like overriding.

Also having a singleton instance class helps us to make a class pretty much like a static class still use OOPs concepts.