Interfaces in Java allow subclasses to be implemented with different data definitions and method implementations. Interfaces are special classes that can be implemented by subclasses. Interfaces do not contain data or method implementations - they only contain abstract method declarations. Interfaces are used to achieve full abstraction and ensure subclasses have consistent method signatures while allowing flexibility in implementation.

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Interface in Java
Interface inJava- Interface isa special classwhichcanbe implementedbysub-classes.So,Interface
isa special classsuitable forgeneralizationof some concreted classesorabstractclasses. Itallows
subclassestobe implementedwithdifferentdatadefinitionandmethodimplementation.
Important Points related to Interface
 Interface isa special classinJava.
 Interface hasno data.
 Interface hasonlyabstract methods(noimplementation)
 Interface is vaguerthanabstract. Abstract isalsovague. Normal classis concrete.
 So,interface hasno data and noimplementation.
Interface Compilation
Whenyoucompile interface program;Aftercompilationinterface programgenerate .classfile.

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Interface is different from a class
 You cannot instantiate aninterface.
 An interface doesnotcontainanyconstructors.
 All of the methodsinan interface are abstract.
 An interface isnotextendedbyaclass;it isimplemented byaclass.
 An interface canextendmultiple interfaces.
Declaring Interfaces:
The interface keywordisusedtodeclare aninterface.Here isasimple example todeclare an
interface:
/* File name : MyInterface.java*/
publicinterface MyInterface
{
//Anynumberof final,staticfields
//Anynumberof abstract methoddeclarations
}
Interface is similar to a class
 An interface cancontainanynumberof methods.
 An interface iswrittenin afile witha.javaextension.
 The byte code of an interface appearsina .classfile.
 Interfacesappearinpackages,andtheircorrespondingbytecode file mustbe inadirectory
structure that matchesthe package name.
Why use Interface
An interface isamechanismtoachieve full abstraction (100%). We can onlydefine abstract
methodsinthe javainterface notmethodbody.Aninterface can'tbe instantiatedjustlikeabstract
classes.