USER-DEFINED CLASSES AND ADTS - Java Programming: From Problem Analysis to Program Design - page 503

public static void incrementY()
{

y++;

}

}
Suppose that you have the following declaration:

Illustrate illusObject = new Illustrate();

The reference variable illusObject can access any public member of the class
Illustrate .
The method incrementY is static and public , so the following statement is legal:

Illustrate.incrementY();
Similarly, because the data member count is static and public , the following state-
ment is legal:

Illustrate.count++;

In essence, public static members of a class can be accessed either by an object, that is, by
using a reference variable of the class type, or using the class name and the dot operator.

8

static Variables (Data Members) of a Class
Suppose that you have a class , say, MyClass , with data members ( static and non-
static ). When you instantiate the objects of type MyClass , only the non- static data
members of the class MyClass become the data members of each object. What about
the memory for the static data members of MyClass ? For each static data member
of the class , Java allocates memory space only once. All MyClass objects refer to the
same memory space. In fact, static data members of a class exist even when no object
of the class type is instantiated. Moreover, static variables are initialized to their
default values. You can access the public static data members outside the class ,as
explained in the previous section.
The following example further clarifies how memory space is allocated for static and
non- static data members of a class.
Suppose that you have the class Illustrate , as given in Example 8-6. Then, memory
space exists for the static data members y and count .
Consider the following statements:

Illustrate illusObject1 = new Illustrate(3); //Line 1

Illustrate illusObject2 = new Illustrate(5); //Line 2

The statements in Lines 1 and 2 declare illusObject1 and illusObject2 to be
reference variables of type Illustrate and instantiate these objects (see Figure 8-15).