Abstract classes are classes that can't be instantiated directly. In other words, you are meant to create subclasses, which you instantiate.
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.
Any class which has one or more abstract methods is called an abstract class. But in the normal class we can't have any abstract methods. We cannot create an object for the abstract classes. When we inherit the abstract class we should implement the abstract method which we inherit.
A final class cannot have any subclasses. An abstract class cannot be instantiated unless it is extended by a subclass.
Abstract class is built to promote inheritance whereas a final class is built to avoid inheritanceAn Abstract class can be extended by another class whereas a final class cannot be extended
Assume a "simple" class be a class without the keyword "abstract".You cannot create an instance of an abstract class. An abstract class is intended to be inherited from (to be extended or derived from).A "simple" class is a class that an instance can be created from (via new operator)
Some 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.
A 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.
Association class is describing the relationship between classes. An abstract class is just 1 class, provides some abstraction behaviors that may be (but do not have to) derived, overridden from.
abstract class no defination used by derieved class where virtual base class is defination that can be overriden later on
In general programming terms, a concrete class is one which can be instantiated, while an abstract class can only be instantiated via a fully implemented subclass.
There is no difference with method declaration and implementation between abstract and non-abstract classes. You do the exact same thing when writing a concrete method in either an abstract or non-abstract class.
Below is the main difference between the 3 components:Concrete class - Provides implementation for all its methods & also for methods from extended abstract classes or implemented interfacesAbstract class - Does not provide implementation for one or more of its methodsInterface - Does not provide implementation for any of its methods
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.
difference between abstract and conclusion
The 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
An 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.
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.
An interface can only have abstract methods or constants in it. A class can have both that and everything else in Java.
The difference between abstract and summary is that an abstract is a short from of a summary.
Some differences are:An abstract class can have code for one or more methods but an interface cannotAll variables in an interface are public static and final but in an abstract class it is notAbstract classes are faster than interfaces
Abstract class is to define "IS_A..." Interface is to define "Behave like ..." (not necessary to be a ...") An abstract class if with all public abstract methods may look just like an interface. An abstract class may also provide some implementation of those APIs (public methods), while an interface is to decouple (separate) the intend from the implementation
An abstract class(or classes) can't have a constructor and hence you cannot invoke the constructor of the class (for example, you can instantiate an abstract class and hence you cannot call the constructor of an abstract class).
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.
An overridden method is one which has already been implemented in the parent class with the same signature but has again been coded in the current class for functionality requirements. An abstract method is one which has only been declared in a class and would have to be implemented by the class that extends this abstract class. The implementation for the method is not available in the class in which it is declared.