Question

I have Java-related question:

I want to know is there a way to create path to class (in program) by using a variable(s).
Im making a program that will download pictures from certain sites and show them to a user. However, different sites have different forms, that’s why I have to define a series of functions specific to each. They cannot be put in the same class because functions that preform same job (just for another site) would have to have same names. I’m trying to make adding support for another site later as simple as possible.

Anyway, the question is, could I call a function in program using a variable to determine its location.

For example: code.picturesite.functionINeed();

code is the package containing all of the coding, and picturesite is not a class but rather a variable containing the name of the desired class – that way I can only change value of the variable to call a different function (or the same function in a different class).

I don’t really expect that to be possible (this was more for you to understand the nature of the problem), but is there another way to do what I’m trying to achieve here?

Answer 1

Yes, there is a way. It’s called reflection.

Given a String containing the class name, you can get an instance like this:

Class<?> c = Class.forName("com.foo.SomeClass");
Object o = c.newInstance(); // assuming there's a default constructor

If there isn’t a default constructor, you can get a reference to one via c.getConstructor(param1.getClass(), param2.getClass(), etc)

Given a String containing the method name and an instance, you can invoke that method like this:

Method m = o.getClass().getMethod("someMethod", param1.getClass(), param2.getClass(), etc);
Object result = m.invoke(o, param1, param2, etc);