What criteria should reference types in the Java programming language meet?

Objects must have a unique identity in memory. References to the same object point to the same location in memory.

They can be assigned to a variable, passed as an argument to a method, and returned from a method as a result.

They can contain fields (instance variables) and methods.

They support inheritance, allowing the creation of class hierarchies.

They support polymorphism, enabling the use of objects of different classes through a single reference.

They implement interfaces, defining behavior contracts.

They use garbage collection for automatic memory management, freeing objects that are no longer referenced.

They can be null, which means the absence of a reference to an object.