Is everything in java running in classes?

Answer 1

Yes, Java is fully object oriented unlike C++ for example.

Answer 2

//You can see Note section in this lesson

https://www.sololearn.com/learn/Java/2137/

Answer 3

If your question was to know whether java is completely an OOP programming language or not then you can read this-

Java is not completely an OOP languages because it supports primitive data types like int, float, double etc.

But Java has something called wrapper classes which are nothing but class type of the primitive types.

Even then it doesn't satisfy the conditions of a complete OOP language because there is autoboxing and unboxing that is happening internally. It means that every wrapper class is converted to its primitive type before performing any operations on the object.