What Is Abstract And Interface In Java

Interface can have only abstract methods. Like in object oriented programming abstraction in java is achieved using abstract classes and interfaces. An abstract class in java is a class that is declared abstract it may or may not contain abstract methods.
what is abstract class and interface in java what is abstract and interface in java

A class can extend only one abstract class while a class can implement multiple interfaces.

What is abstract and interface in java. Java 18 interface can have static and default methods. Interface supports multiple inheritance. Interfaces are blueprint like class but it will have only the method declaration. An interface is a blueprint used to implement a class.

In an interface keyword abstract is optional to declare a method as an abstract. Section 9111 of java language specification mentions that every interface is implicitly abstract whether you type in the abstract modifier or not. An abstract class permits you to make functionality that subclasses can implement or override whereas an interface only permits you to state functionality but not to implement it. In abstract class keyword abstract is mandatory to declare a method as an abstract.

It wont have any method of implementation. An interface in java is implicitly abstract and adding that modifier is considered redundant and makes no difference. However the interface offers full abstraction in java something that abstract classes cannot do. A java interface can be implemented using keyword implements and abstract class can be extended using keyword extends.

An interface can extend another java interface only an abstract class can extend another java class and implement multiple java interfaces. 2 abstract class doesnt support multiple inheritance. So if you cant define anything why we need an interface. It is a collection of abstract methods and contains no concrete methods unlike abstract class.

All the methods in the interface are public abstract by default. It is quite similar to a java interface except that fact that it can contain default method implementation. An abstract class can have protected and public abstract methods. Since java 8 it can have default and static methods also.

By rule all method inside interface must be abstract well this rule is changing in java 8 to allow lambda expressions now interface can have one non abstract method also known as a default method. 3 abstract class can have final non final static and non static variables. This modifier is obsolete and should not be used in new programs. An interface can have only have public abstract methods.

1 abstract class can have abstract and non abstract methods.