What data types in Java are considered reference types, and how do they differ from primitive types?

In Java, reference data types include all objects and arrays. This includes, for example, classes (String, Integer, user-defined classes), interfaces, arrays, and enums.

The main difference between reference types and primitive types:

• Primitive types (int, boolean, char, double, etc.) store the actual values directly in memory.
• Reference types store in the variable not the value itself, but a reference (address) to the object in the heap.

This affects behavior during assignment and method passing: with primitives, the value is copied, but with reference types, the reference to the object is copied, so changes to the object inside the method are reflected outside as well.