Instantiate from .java file

I would like to instantiate a list of objects from a certain directory without previous knowledge of their existence. I do however know that the classes all inherit from the same parent.

Directory

Some.java 
SomeOther.java 
YetAnother.java

I have tried to use the URLClassLoader as such:

URLClassLoader.newInstance(new URL[]{file.toURI().toURL()})

But cannot create the class because I do not know its name in advance.

How can I create an array of objects from a list of .java files.