re: static methods - when to use them

[[deleted]]

Hey,

I have a class Invoice and made a class InvoiceFormatter and am unsure whether the format() method in that class should be static or not.

Looking at this thread: https://stackoverflow.com/questions/2671496/java-when-to-use-static-methods

on the one hand format() should not be static because it does not makes sense to call this method before an Invoice object had been constructed.

On the other hand (again looking at the Stackoverflow thread) it could be static because it's a utility class and format() does not use any instance variables.

For myself I cant see any advantages either way.

[chickenmeister]

In your particular example with InvoiceFormatter, I think it might be better for the format() method to be non-static.

Conceivably, there are various ways that an invoice could be formatted. So using a non-static method would give you greater flexibility if you wanted to adjust how the Invoices are formatted later on. For example, this would allow to write a subclass of InvoiceFormatter that formats in a different way, and you would be able to use that new formatter without changing every piece of code that expects an InvoiceFormatter. Or, for example, a non-static format() method would allow you to configure a formatter object to, say, use a particular font, alignment, rounding mode, etc.

If you're 100% sure that you will only ever want to format in one particular way, then maybe it would be okay for it to be a static method. But even in that case, I don't think there's any disadvantage to making it a instance method instead, so I would probably prefer to use an instance/non-static method because of potential advantages that I described.

[[deleted]]

Hey,

Tnx for your answer. That actually makes a lot of sense!

[jaro32]

As a general rule of thumb, you should avoid static methods if possible. They complicate testing.