Non-Primitive Types

Because non-primitive data types make references to things, they are also known as reference types.

Primitive and non-primitive data types differ primarily in the following ways:

• Primitive types are predefined (already defined) in Java. Non-primitive types are created by the programmer and is not defined by Java (except for String).
• Non-primitive types can be used to call methods to perform certain operations, while primitive types cannot.
• A primitive type has always a value, while non-primitive types can be null.
• A primitive type starts with a lowercase letter, while non-primitive types starts with an uppercase letter.

Arrays, Classes, Interfaces, Strings, and so on are instances of non-primitive types. A later chapter will cover these in more detail.