Abstract class and an Interface.

Type of methods: Interface can have only abstract methods. Abstract class can have abstract and non-abstract methods. From Java 8, it can have default and static methods also. Final Variables: Variables declared in a Java interface are by default final. An abstract class may contain non-final variables. Type of variables: Abstract class can have final, non-final, static and non-static variables. Interface has only static and final variables. Implementation: Abstract class can provide the implementation of interface. Interface can’t provide the implementation of abstract class. Inheritance vs Abstraction: A Java interface can be implemented using keyword “implements” and abstract class can be extended using keyword “extends”. Multiple implementation: An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces. Accessibility of Data Members: Members of a Java interface are public by default. A Java abstract class can have class members like private, protected, etc.

Class can extend only one abstract class and class can implement numerous interface.

Probably "Difference Between abstract Class and Interface" is the most frequent question being asked in .Net world . In this tutorial, I will explain the difference theoretically followed by code snippet. Theoretically there are basically 5 differences between Abstract Class and Interface which are listed as below :- A class can implement any number of interfaces but a subclass can at most use only one abstract class. An abstract class can have non-abstract Methods(concrete methods) while in case of Interface all the methods has to be abstract. An abstract class can declare or use any variables while an interface is not allowed to do so. So following Code will not compile :- interface TestInterface { int x = 4; // Filed Declaration in Interface void getMethod(); string getName(); } abstract class TestAbstractClass { int i = 4; int k = 3; public abstract void getClassName(); } It will generate a compile time error as :- Error 1 Interfaces cannot contain fields . So we need to omit Field Declaration in order to compile the code properly. interface TestInterface { void getMethod(); string getName(); } abstract class TestAbstractClass { int i = 4; int k = 3; public abstract void getClassName(); } Above code compiles properly as no field declaration is there in Interface. An abstract class can have constructor declaration while an interface can not do so. So following code will not compile :- interface TestInterface { // Constructor Declaration public TestInterface() { } void getMethod(); string getName(); } abstract class TestAbstractClass { public TestAbstractClass() { } int i = 4; int k = 3; public abstract void getClassName(); } Above code will generate a compile time error as :- Error 1 Interfaces cannot contain constructors So we need to omit constructor declaration from interface in order to compile our code . Following code compile s perfectly :- interface TestInterface { void getMethod(); string getName(); } abstract class TestAbstractClass { public TestAbstractClass() { } int i = 4; int k = 3; public abstract void getClassName(); } An abstract Class is allowed to have all access modifiers for all of its member declaration while in interface we can not declare any access modifier(including public) as all the members of interface are implicitly public. Note here I am talking about the access specifiers of the member of interface and not about the interface. Following code will explain it better :- It is perfectly legal to give provide access specifier as Public (Remember only public is allowed) public interface TestInterface { void getMethod(); string getName(); } Above code compiles perfectly. It is not allowed to give any access specifier to the members of the Interface. interface TestInterface { public void getMethod(); public string getName(); } Above code will generate a compile time error as :- Error 1 The modifier 'public' is not valid for this item. But the best way of declaring Interface will be to avoid access specifier on interface as well as members of interface. interface Test { void getMethod(); string getName(); }

Abstrac class is used to write static method and use it in through out application. Interface is used to declare proto type only

Example on Interface and Abstract interface common { void sms(); void calling(); } interface asb { } abstract class features { public void internetaccess() { } //declare abstract methods here } public class Nokia2690 : features, common,asb { //common methods should have body here //if it is abstract methods should be definition here //if it is concrete methods may or may not be //No need to create object for abstract and interfaces u can take number of interfaces }

Abstract Class V/s Interface (1) :-Abstract class can have implementation for some of its method. But the interface can't have implementation for any of its method. (2) :-Abstract class can have field but interface does not have fields. (3) :-An Interface can inherit from another interface only can't inherit from another abstract class but an abstract class can inherit from another abstract class and another interface. (4) :-Abstract class members can have access modifiers where interface member doesn't have access modifiers. You can go on this link for more difference.. http://dotnet-munesh.blogspot.in/2013/12/difference.html