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What are the differences between an abstract class and an interface in java?
Wiki User
∙ 12y ago
They are very different.
An abstract class is a class that represents an abstract concept (Google define "abstract" if you're unsure) such as 'Thoughts' or 'BankAccount'. When a class is defined as abstract it cannot be used (directly) to create an object. Abstract classes are used as super-classes so that all of their subclasses inherit all methods.
Interfaces can be thought of as contracts with all of their implementing classes. They simply require all implementing classes to have methods with the same signature as that defined in the interface, but such methods can behave as appropriate.
Hope that helps :)
Wiki User
∙ 13y ago
Wiki User
∙ 12y agoAn abstract class can have a combination of abstract methods and normal methods.
Interfaces cannot implement any methods themselves, all have to be abstract.
Other classes can extend only one class (abstract or not), but can implement as many interfaces as they want.
Wiki User
∙ 13y agoSome difference between an interface and an abstract class are:
a. All variables in an interface are public, static and final but that is not the case in abstract classes
b. An abstract class can have both abstract and concrete methods but an interface cannot have concrete methods
c. An abstract class can extend other classes and implement interfaces, while an interface can only extend other interfaces.
Wiki User
∙ 12y agoAn interface is like a 100% abstract class. Only abstract methods can go in an interface. In addition, all methods in an abstract class are public and abstract by default. You "extend" an interface using the keyword implements. You can implement multiple interfaces, but you have to extend only one class. An interface can have only constants. This means no instance variables.
As for an abstract class, you can put both abstract and concrete methods in an abstract class. It can have instance variables, but you can only extend one abstract class.
Sun recommends using abstract and concrete class extension to signify what a class is, with an example in the following inheritance tree:
Object
|
|-Person
|
|-Programmer
|
|-JavaProgrammer
An interface is for signifying what jobs a class can do, like a Message class implementing a Sendable interface. Also, class names should be nouns and interface names should be adjectives, but conventions vary widely among programmers.
Wiki User
∙ 12y agoInterface - to act like, to behave like, defines publicmethods/contracts. Maybe extended by different class hierarchies, in single inheritance or multiple inheritance.
abstract class - IS_A, is/derived from [an abstraction], defines abstract methods (not necessary public) to force the derived classes to implement them. It also may provide data members and other methods to be inherited and overridable. Maybe extended by 1 class hierarchy (single inheritance) (Java, C#, VB.Net), or some in multiple inheritance (C++).
Wiki User
∙ 12y agoA more prcise description of difference is as follows.... an interface is a specification of a set of methods that the implementation class must adhere to, while an abstract class is indeed an implementation class albeit a class that is not concrete, i.e., one cannot directly instantiate an abstract class.
Wiki User
∙ 13y agoComparison between an Abstract Class and an Interface:
While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict:
• All interface methods are implicitly public and abstract. In other words, you do not need to actually type the public or abstract modifiers in the method declaration, but the method is still always public and abstract. (You can use any kind of modifiers in the Abstract class)
• All variables defined in an interface must be public, static, and final-in other words, interfaces can declare only constants, not instance variables.
• Interface methods must not be static.
• Because interface methods are abstract, they cannot be marked final, strictfp, or native. (More on these modifiers later.)
• An interface can extend one or more other interfaces.
• An interface cannot extend anything but another interface.
• An interface cannot implement another interface or class.
• An interface must be declared with the keyword interface.
You must remember that all interface methods are public and abstract regardless of what you see in the interface definition.
Wiki User
∙ 12y agoThe difference are:
- An abstract class can have methods that actually have code inside them whereas an Interface cannot (An Interface can be thought of as a 100% pure abstract class)
- All variables in an Interface are public, static, final whereas that is not the case in Abstract classes
Wiki User
∙ 12y agoAn abstract class may contain code in method bodies, which is not allowed in an interface. With abstract classes, you have to inherit your class from it and Java does not allow multiple inheritance. On the other hand, you can implement multiple interfaces in your class.
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Difference between interface and abstract class on uml?
In general, the differences are that interface has(1) no fields and(2) no implementation of methodsbut in UML interface may have features (fields), so the difference left is that interface in UML has no implemented methods while abstract class by definition is partially implemented class.
What is difference between abstract class and interface in core java give brief answer with example?
Differences:Abstract class can also contain method definitions but an interface can contain only declarationsAll variables in an interface are by default public static and final whereas in Abstract class it is notAn interface can be considered as a pure abstract class that contains no method implementations and contains only declarations.
What is similarities between Abstract Class and Interface?
If a class has one abstract method ,the class has to be an abstract class.Methods can be implemented in abstract class.Whereas a interface is like a abstract class...the only difference being that the methods are never implemented in Interface.
What is an interface class and what is an abstract class?
The term interface class does not exist in C#. If this is a term describing a class being an interface to other component (human, subsystems, etc), it is very application specific. The designer of that application should know the abstraction.However, C# does have another type called interface. An interface is NOT a class. An interface defines the intention of some behaviors that classes may be extended it and provides the implementation. The intention, is nothing but method signatures, which defines the return data type, the method name, and any method arguments and associated data type. The implementation is the code of the method. Interface is used for separating the concern of design and implementation.Abstract class is a class with abstract keyword. It can be just like a class without that keyword (then, why it is an abstract class?). But it may have some methods or properties defined as abstract. These abstract methods, like the method signatures of an interface, defines the intention.The subclasses of such an abstract class would need to implement those abstract methods (providing the code).There are more common, differences between interfaces and abstract classes, please see answer(s) of those related questions in C# category.
What is the difference between an interface and an abstract class?
We can't instantiate both interfaces and abstract classes.The only one difference between them is that an interface can't contain concrete(fully defined) methods where as an abstract class may contain them.An abstract class not necessarily contain abstract methods. we can make a class as abstract class even it does not has any abstract methods.When there is a need to write both abstract and concrete methods in a single unit we have to use an abstract class instead of an interface since an interface cant contain concrete methods.All the fields(or properties) of an interface are by default 'static final' even when you don't mention explicitly. And all methods are 'public abstract'.But in an abstract class we can have any type of fields and methods.
Difference between interface and abstract class on uml?
In general, the differences are that interface has(1) no fields and(2) no implementation of methodsbut in UML interface may have features (fields), so the difference left is that interface in UML has no implemented methods while abstract class by definition is partially implemented class.
What is difference between abstract class and interface in core java give brief answer with example?
Differences:Abstract class can also contain method definitions but an interface can contain only declarationsAll variables in an interface are by default public static and final whereas in Abstract class it is notAn interface can be considered as a pure abstract class that contains no method implementations and contains only declarations.
What is similarities between Abstract Class and Interface?
If a class has one abstract method ,the class has to be an abstract class.Methods can be implemented in abstract class.Whereas a interface is like a abstract class...the only difference being that the methods are never implemented in Interface.
What is the major difference between an Interface and a Class?
An interface can only have abstract methods or constants in it. A class can have both that and everything else in Java.
What is an interface class and what is an abstract class?
The term interface class does not exist in C#. If this is a term describing a class being an interface to other component (human, subsystems, etc), it is very application specific. The designer of that application should know the abstraction.However, C# does have another type called interface. An interface is NOT a class. An interface defines the intention of some behaviors that classes may be extended it and provides the implementation. The intention, is nothing but method signatures, which defines the return data type, the method name, and any method arguments and associated data type. The implementation is the code of the method. Interface is used for separating the concern of design and implementation.Abstract class is a class with abstract keyword. It can be just like a class without that keyword (then, why it is an abstract class?). But it may have some methods or properties defined as abstract. These abstract methods, like the method signatures of an interface, defines the intention.The subclasses of such an abstract class would need to implement those abstract methods (providing the code).There are more common, differences between interfaces and abstract classes, please see answer(s) of those related questions in C# category.
What is the difference between an interface and an abstract class?
We can't instantiate both interfaces and abstract classes.The only one difference between them is that an interface can't contain concrete(fully defined) methods where as an abstract class may contain them.An abstract class not necessarily contain abstract methods. we can make a class as abstract class even it does not has any abstract methods.When there is a need to write both abstract and concrete methods in a single unit we have to use an abstract class instead of an interface since an interface cant contain concrete methods.All the fields(or properties) of an interface are by default 'static final' even when you don't mention explicitly. And all methods are 'public abstract'.But in an abstract class we can have any type of fields and methods.
Abstract class vs interface?
Comparison between an Abstract Class and an Interface:While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict:
What is difference between interface and abstract class?
All the methods declared inside an Interface are abstract. Where as abstract class must have at least one abstract method and others may be concrete or abstract. In Interface we need not use the keyword abstract for the methods.
Why instance in abstract or interface?
we can make object of interface but in abstract we can not make object of it interface ab= new Classs(): in interface we maintain multiple inhetence by use of obj of interface we if inherit two class have same fun then we give the name of that interface and call the pertucular that fun interface ab= new class() ab.add(); but in Astract Class we cannot make object of it only class class wich inherit it can make object class ab2= new Class(); and by obj we call function of drived class ob2.add();
What is difference between interface and abstract in java?
While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict: • All interface methods are implicitly public and abstract. In other words, you do not need to actually type the public or abstract modifiers in the method declaration, but the method is still always public and abstract. (You can use any kind of modifiers in the Abstract class) • All variables defined in an interface must be public, static, and final-in other words, interfaces can declare only constants, not instance variables. • Interface methods must not be static. • Because interface methods are abstract, they cannot be marked final, strictfp, or native. (More on these modifiers later.) • An interface can extend one or more other interfaces. • An interface cannot extend anything but another interface. • An interface cannot implement another interface or class. • An interface must be declared with the keyword interface. You must remember that all interface methods are public and abstract regardless of what you see in the interface definition.
When an interface method is implemented in a class it must be declared as?
Abstract type
When do you give preference to abstract classs and interface?
Abstract class provides a way of "being a [something like me]", or inheritance interface provides a set of functionality (contract) as "behaving". Abstract class provides the single inheritance and perhaps some default implementation, while interface may be implemented by different classes that have nothing to do one and other except the common interface implementation. The preference I would start with: Ask yourself that an object should be "Is a something or behave like something". If your answer is "Is a", then abstract class is more likely your good choice. But if your answer is behave like, does not need to Is a, then the interface is the way to go.
