In Java polymorphism can be of following types:
Interface and Method Overriding
Or we can also say that a polymorphism is possible in both state Static and Dynamic. Coz polymorphism means in many forms.
So do not get confused of it just learn the functionalities and how they work! If you want to read the theory first then visit http://www.roseindia.net/java/master-java/java-object-oriented-language.shtml