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Class Interface Interface

An interface in Java is a blueprint of a class that defines abstract methods but does not define method bodies. Interfaces are used to achieve abstraction and multiple inheritance in Java. A class implements an interface to inherit its abstract methods, while an interface can extend another interface. An interface is declared using the "interface" keyword and can only contain abstract methods and static constants.

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59 views2 pages

Class Interface Interface

An interface in Java is a blueprint of a class that defines abstract methods but does not define method bodies. Interfaces are used to achieve abstraction and multiple inheritance in Java. A class implements an interface to inherit its abstract methods, while an interface can extend another interface. An interface is declared using the "interface" keyword and can only contain abstract methods and static constants.

Uploaded by

Banani Bhattacharya
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Interface

An interface in Java is a blueprint of a class. It has static constants and abstract


methods.

The interface in Java is a mechanism to achieve abstraction. There can be only


abstract methods in the Java interface, not method body. It is used to achieve
abstraction and multiple inheritance in Java.

The interface keyword is used to declare an interface.

Syntax : Declare interface


interface <interface_name> {

// declare constant fields(e.g- final int a = 10;)


// declare abstract methods (e.g-void display();)<-no method body only
declaration
}
A class extends another class, an interface extends another interface, but a class
implements an interface.

class interface interface

extends implements extends

class class interface

Syntax: Implementing interface


interface Intf
{
void show(); // only declared not defined i.e abstract method
}
class Clnew implements Intf //Clnew is implementing Intf i.e inheriting
{
public void show()
{
System.out.println("Hello"); // subclass is defining the method
}
public static void main(String args[])
{
Clnew obj = new Clnew(); // object of interface can’t be created i.e
can’t be instantiated, object of subclass is created.
obj.show();
}
}

CLASS INTERFACE
The keyword used to create a class is The keyword used to create an interface is
“class” “interface”
A class can be instantiated i.e, An Interface cannot be instantiated i.e,
objects of a class can be created. objects cannot be created.
Class does not support multiple Interface supports multiple inheritance.
inheritance.
It can be inherited by another class.It cannot inherit a class.
It can be inherited by another class It can be inherited by a class by using the
using the keyword ‘extends’. keyword ‘implements’ and it can be
inherited by an interface using the
keyword ‘extends’.
It can contain constructors. It cannot contain constructors.
It cannot contain abstract methods. It contains abstract methods only.
Variables and methods in a class can All variables and methods in a interface are
be declared using any access declared as public.
specifier (public, private, default,
protected)
Variables in a class can be static, All variables are static and final.
final or neither.

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