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.

Polymorphism means poly multiple forms. Many shapes. In object oriented programming, polymorphism means the type of object is determined as late as at runtime. What does it mean, and what do we achieve by this? Let us take an example. We have following classes.

Polymorphism, i.e. runtime type determination, is very important in Java. Polymorphic programming is generic programming. Here we are not calling methods of concrete classes at the time of coding, instead we are writing generic code, that can allow us to assign desired concrete instances at runtime. Let us take an example-
java.util.List interface represents all lists and is extension of java.util.Collection interface. Concrete implementations are java.util.ArrayList, java.util.LinkedList, java.util.Vector. While writing code you take a freedom of using the generic type i.e. List. But at runtime, based on some parameter you determine …