Short answer is yes, if you have only one inventory and one shop it
doesn't matter.
*BUT* if you want to do things properly, it does matter.

Think about real world: we have for example the class "human being" that
is the category that contains all the people in the world.
Keep in mind that the class is a *category*, not something "you can touch".

Now a static method or variable, is something that refers to the
category, not to one particular object in the category.
In this example, we could have

  static final int NUMBER_OF_EYES = 2;

it's static, it's a class variable because all human beings have 2 eyes.

On the other hand, if you are referring to an action or a property that
 is about one (or some) instances of the category, then it's not static
but an instance method/field.
For example:

  String colorOfHairs = "red";

Because someone has red hairs, but this is different for each people.

To get back to your case, you should create an instance of your
shop/inventory and call non-static methods, even if you have only one of
them.

You should always think about real world and ask yourself: "is this
something about the category or about one particular object in the
category?"

This is probably the single most important thing to understand in
object-oriented programming.
I suggest you take ten minutes to do a simple exercise: you write down
on a piece of paper some classes (for ex. "vehicle", "building", etc.)
then you try to identify five instance variables/methods and five static
variables/methods for each one.

I hope my explanation was not too intricated :-)

Francesco

You should realize that other people in this thread seem to have moved
on and started talking about whether these methods should be static or
not.  That's a good question, but it's not exactly what you asked.

Since the methods are static, you should NOT create an object of class
Inventory to call them.  Doing so is very confusing.  The object won't
be used at all, and you'll just be calling static methods, but lying to
people reading your code by pretending to call non-static methods.  It
was a mistake by Sun in the language specification to allow you to to do
so.  Several popular Java development environments will give warnings
from the compiler if you do it.

So if you want to take Francesco's advice, then change the methods (and
data they operate on) so they aren't static and THEN create the object
and call the functions.  But if you leave the methods static, you should
call them like they are static methods... that is, "Inventory.status()"
and so on.