Class: A class is a
non-primitive datatype that contains member variables (data) and member
functions (methods) that operates on the variables. A class is declared by the use of the class
keyword. The general form of class
definition is as follows.
Syntax: class class-name
{
datatype
instance-variable1;
datatype
instance-variable2;
-
-
datatype
instance-variablen;
datatype
methodname1(parameter-list)
{
//
method body
}
-
-
datatype
methodnamem(parameter-list)
{
//
method body
}
}
The
data, or variables defined with in a class are called instance variables. The code is present with in methods. Collection of methods and variables defined
with in a class are called members of the class.
Example: class box
{
double
width, height, depth;
double
volume( )
{
return
width*height*depth;
}
}
Object: Object is an instance of the
class. By means of the object only, we
can access the functions (methods).
main(
)
{
box
a = new box( );
a.volume();
}
Comments in a Program: Three types of
comment statements are available in Java.
They are
i)
Single line comment (//)
ii)
Multi line comment (/* and */)
iii)
Documentation comment (/** and */)
1. Single line comment:
For a single line comment we use double slash (//) to begin a comment. It ends at the end of line.
Example: // Program for stack operations
2. Multi line comment:
For more than one line of information, we use multi line comments. Multi line comments are starts with /* and
ends with */.
Example: /* Program for stack operations
Designed by Dev
Developer */
3. Documentation comment:
For the documentation purpose, we use documentation comments. Documentation comments are starts with /**
and ends with */.
Example: /** A test for JDK
@
Author S.Satya
@
version 1.0 */
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