Question

I may be wrong as I have not got too much experience with Java, but here is a question.

I have a class which contains many methods (basically it is a simple library).

I create an object of this class let’s say MyLibrary obj = new MyLibrary(parameters);

The parameters set up any necessary functionality for the library to run correctly.

Then I can call obj.getSomething/obj.setSomething/obj.createSomething etc etc…

In my main class I really need only one this kind of library object.

Now… Would it be more useful for me not to use it as an object, but put it as extends and then create a function inside of the library like a constructor which I would call manually?

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EDIT:

The relation between the one class and MyLibrary is very close. Basically, I have many classes which do similar things but have some different higher layer functionality. So I separated method which must be in all those classes.

It seems it is very similar to shape class and triangle, circle, square example. So MyLibrary is similar to shape which contains all the foundation.

Answer 1

What you described strongly resembles a utility class, similar to Java’s Collections. The class has only static methods, and a private constructor to prevent instantiations. This is a well-known idiomatic pattern in Java – you can use it to create your own groups of methods providing related functionality.

You should not extend, or even instantiate, utility classes at all. Starting with Java-5, you can statically import them so that you could use their methods without making an explicit reference to their class.