Is Java a pure object-oriented programming language ?

 NO. 

A programming language is called pure object-oriented programming (OOP) language only if it treats everything inside a program as objects. 

   There are the following qualities defined for a language to be a pure object-oriented language:

• It must support OOP features such as 
•  Inheritance
•  Abstraction
•  Encapsulation/Data Hiding
•  Polymorphism    

• Every user-defined or predefined types should be an object

    Since Java supports OOP features but it also supports primitive data types that is why Java is not a pure object-oriented programming language. 

 Java consists of Eight primitive data types which are:

        byte, boolean, short, char, int, float, long, double

Note: While String in Java is a non-primitive data type.

        Hence Wrapper Classes are defined to covert primitive data types into an object and vice-versa.