Interface

Interface

• Java does not support multiple inheritance means that classes in java can not have more than one super class.
•  Java provides an alternet approach known as interface to support the concept of multiple inheritances.
• Interface is syntactically similar to classes but they contain instance variable and their methods are declared without anybody.
• The major difference between class and interface is that interface defines only abstract methods and final fields.
• Interface is designed to support dynamic method resolution at runtime.
•  It is the responsibility of the class that implements an interface to define the code for implementation of these methods.

Syntax:

interface interface-name

{

variable declaration;

method declaration;

}

• Here, interface is the keyword and interface name is any valid java identifier.

•  Here all variables are declared as constant.
•  Method declaration will contain only a list of methods without any statements.
•  Methods in interface have no definition.
• Variable declared inside the interface are implicitly final and static so it cannot be changed by implementing a class.

Implementing an interface.

• Interfaces are used as superclass whose properties are inherited by a class.

Syntax

Class classname extends superclass implements interface1,interface2

{

body of class

}

• We can implement number of interface.
•  When a class implements more than one interface they are represented by comma.