Beginning Java Objects: Chapter 3
Objects and Classes
Instantiation
A class definition may be thought of as a template for creating software objects — a 'cookie cutter' used to:
- Stamp out a prescribed data structure in memory to house the attributes of a new object.
- Associate a certain set of behaviors with that object.
The term instantiation is used to refer to the process by
which an object is created/constructed based upon a class
definition. From a single class definition — for example,
Student — we create many objects/instances of
the class, in the same way that we use a single cookie cutter to
make many cookies. Another way to refer to an object, then, is as
an instance of a particular class. We'll talk about the
physical process of instantiating objects as it occurs in
Java in a bit more detail later in this chapter.
Classes may be differentiated from objects, then, as follows:
- A class defines the attributes — names and data types — that all objects belonging to the class
must possess, and the methods that all objects belonging to the class must be able to perform,
and can be thought of as an empty template.
- An object, on the other hand, is a filled-in template to which attribute values have been provided.
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