These articles explain the object oriented concepts in detail. UML representation of most of the concept is provided in these articles. Also Java code examples are available to explain the concepts better.  Here is the list of articles.

Abstraction – you can call it as generalization. Generalization means removing specific information to make that object represent a familiy of all similar objects. Obviously we leave specific things aside to consider them in specific objects, which may be derived from this general object, which is our abstract object. Let us take an example (you may be knowing this example already).