An interface is a reference kind in Java. It is similar to class. It is a set of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface.
Alongside abstract methods, an interface may also contain constants, default methods, static methods, and nested types. Method bodies exist only for default methods and static methods.
Writing an interface is much like writing a category. however a category describes the attributes and behaviors of an item. And an interface contains behaviors that a class implements.
Unless the class that implements the interface is summary, all the methods of the interface need to be defined in the class.
An interface is similar to a class in the following ways −
However, an interface is different from a class in several ways, including −
The interface keyword is used to declare an interface. Here is a simple example to declare an interface −
Following is an example of an interface –
Interfaces have the following properties −
While a class implements an interface, you can think of the class as signing a contract, agreeing to carry out the unique behaviors of the interface. If a class does not perform all the behaviors of the interface, the class needs to claim itself as abstract.
a class uses the implements keyword to implement an interface. The implements keyword appears in the class declaration following the extends portion of the declaration.
This will produce the following result −
When overriding methods defined in interfaces, there are several rules to be followed −
When implementation interfaces, there are several rules −
An interface can extend another interface in the same way that a class can extend another class. The extends keyword is used to extend an interface, and the child interface inherits the methods of the parent interface.
The following Sports interface is extended by Hockey and Football interfaces.
The Hockey interface has four methods, but it inherits two from Sports; thus, a class that implements Hockey needs to implement all six methods. Similarly, a class that implements Football needs to define the three methods from Football and the two methods from Sports.
A Java class can only extend one parent class. Multiple inheritance is not allowed. Interfaces are not classes, however, and an interface can extend more than one parent interface.
The extends keyword is used once, and the parent interfaces are declared in a comma-separated list.
For example, if the Hockey interface extended both Sports and Event, it would be declared as −
The most common use of extending interfaces occurs when the parent interface does not contain any methods. For example, the MouseListener interface in the java.awt.event package extended java.util.EventListener, which is defined as −
An interface with no methods in it is known as a tagging interface. There are two primary design purposes of tagging interfaces −
Java Related Interview Questions
|File Maker Interview Questions||J2EE Interview Questions|
|Core Java Interview Questions||Android Interview Questions|
|JavaServer Faces (JSF) Interview Questions||Java Swing Interview Questions|
|JavaMail API Interview Questions||Java collections framework Interview Questions|
|Java 8 Interview Questions||Java Collections Interview Questions|
|Java Exception Handling Interview Questions||Java Concurrency Interview Questions|
|Java String Interview Questions||Java Hadoop Developer Interview Questions|
|Java Serialization Interview Questions||Java Programmer Interview Questions|
|Java Inheritance Interview Questions||Java IO Interview Questions|
|Hadoop Testing Interview Questions|
All rights reserved © 2018 Wisdom IT Services India Pvt. Ltd
Wisdomjobs.com is one of the best job search sites in India.