They are so-called because they refer to any particular object. Unlike the primitive data types, the non-primitive ones are created by the users in Java. Examples include arrays, strings, classes, ...

Non-Primitive Data Types are called Java Objects or Java Classes. String, Scanner, etc. are non-primitive data types (objects). The Java API gives us these objects (for free!). In Java, you make your ...

This capability lets us program at a higher level of abstraction (classes and objects) rather than focusing separately on data structures ... one parameter differs in type. For example, consider ...

Even the most complicated classes in Java can be flattened down to nothing more than the set of primitive data types they represent. But primitive types aren’t objects, and that presents a problem.