Interface is a collection of method
declaration and constants that one or more classes of objects will use. Interface definition is same as class except
that it consists of the methods that are declared have no method body. They end with a semicolon after the parameter
list. Syntax for an interface is as
follows.
Syntax: <access specifier>
interface <it-name>
{
type
varname1=value;
type
varname2=value;
.
.
returntype
method-name1(parameter-list);
returntype
method-name2(parameter-list);
.
.
}
Here,
Ø access
specifier is public or not used. public
access specifier indicates that the interface can be used by any class. Otherwise, the interface will accessible to
class that are defined in the same package as in the interface.
Ø interface
keyword is used to declare the class as an interface.
Ø it-name
is the name of the interface and it is a valid identifier.
Ø Variables
declared inside the interface are implicitly final and static. They cannot be changed in the implementing
class.
Ø All
the methods in an interface are implicitly abstract methods. Method implementation is given in later
stages.
Ø The
main difference between a class and interface is class contains methods with
method body and the interface contains only abstract methods.
Example:
public interface shape
{
int
radius=2;
public
void area(int a);
}
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