Java offers mechanisms to create objects and methods to design
interfaces for those objects to communicate.

The java  language provides mechanisms to enforce the Object Oriented
model by defining encapsulation, inheritance and polymorphism.

So we can say that Java is an Object Oriented language. But, still
there many debates saying it is not OOP.

Refer some of these sites. These are some of very good discussions on
whether Java is OOP or not...

http://c2.com/cgi/wiki?IsJavaObjectOriented

saloon.javaranch.com/cgi-bin/ubb/ultimatebb.cgi?
ubb=get_topic&f=9&t=000146