A Quick Tour - The Java Programming Language - page 20

1.7.1. Creating Objects
Objects are created by expressions containing the new keyword. Creating
an object from a class definition is also known as instantiation; thus, ob-
jects are often called instances.
Newly created objects are allocated within an area of system memory
known as the heap. All objects are accessed via object references any
variable that may appear to hold an object actually contains a reference
to that object. The types of such variables are known as reference types,
in contrast to the primitive types whose variables hold values of that
type. Object references are null when they do not reference any object.
Most of the time, you can be imprecise in the distinction between actual
objects and references to objects. You can say, "Pass the object to the
method" when you really mean "Pass an object reference to the meth-
od." We are careful about this distinction only when it makes a differen-
ce. Most of the time, you can use "object" and "object reference" inter-
changeably.
In the Point class, suppose you are building a graphics application in
which you need to track lots of points. You represent each point by its
own concrete Point object. Here is how you might create and initialize
Point objects:
Point lowerLeft = new Point();
Point upperRight = new Point();
Point middlePoint = new Point();
lowerLeft.x = 0.0;
lowerLeft.y = 0.0;
upperRight.x = 1280.0;
upperRight.y = 1024.0;
middlePoint.x = 640.0;
middlePoint.y = 512.0;