Learn Java for Web Development

APPENDIX A: Introduction to Java 385

instance methods. Instance variables and instance methods, which belong to objects, are called
instance members (see Listing A-6) to distinguish them from static members, which belong only to
the class.

Listing A-6. The Instance Members

1. class ClassA{


2. // instance Members


3. int i ; // instance variable


4. void methodA(){// instance method


5. // do something


6. }


7. }

   In line 3, i is an instance variable of type int, and int is the primitive

data type of i.

   In line 4, methodA(){} is an instance method.

Static Members

Static members, declared with the keyword static, are the members that belong only to the class and
not to any specific objects of the class. A class can have static variables and static methods. Static
variables are initialized when the class is loaded at runtime. Similarly, a class can have static methods
that belong to the class and not to any specific objects of the class, as illustrated in Listing A-7.

Listing A-7. Static Members

1. class ClassA{


2. static int i ;


3. static void methodA(){


4. // do something


5. }


6. }

Unlike instance members, static members in a class can be accessed using the class name,
as shown here:

ClassA.i // accessing static variable in Line 2 of Listing A-7

ClassA.methodA(); // accessing static method in Line 3 of Listing A-7

Though static members in a class can be accessed via object references, it is considered bad
practice to do so.