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Answered 2009-10-25 04:34:41

An abstract class is one that has one or more abstract methods. i.e., methods that have only a declaration and no implementation.

A fully abstract class is one that has only abstract methods and does not provide implementation to even one method in the class. A fully abstract class is equal to an interface.

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The keyword abstract is used to signify a class which does not offer the method definition for one or more methods in the class. A fully abstract class is equivalent to an interface.


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.


You can't put an abstract method (pure-virtual method) in a normal class because the normal class would become abstract itself. Only non-abstract classes can be physically instantiated as objects, and only if they fully implement all the abstract methods inherited from their base classes.


Abstract classes are to be extended until to a concrete class.Can have both abstract & non abstract methods.An Abstract class can not be instantiated.A non abstract class can be extended to an abstract class.If At least one abstract method present in a class then that class must be abstract.abstract & final modifiers can never be together.abstract classes can have both abstract methods & non abstract methods.


Yes an abstract class can inherit from another abstract class but all the methods of the base abstract class must be abstract.


//We Declare an abstract class as-abstract class Car{}//Example of an abstract methodabstract void hondaCity(); //no method body and abstract//Example of Abstract class that has an abstract methodabstract class Car{abstract void run();}class HondaCity extends Car{void run(){System.out.println("runs smartly");}public static void main(String args[]){Car obj = new HondaCity();obj.run();}}//OUTPUT will be-runs smartly


An abstract factory class is a class which has an abstract method to create an object.


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 abstract class is nothing but class which contains both abstract and concrete methods for abstract class we r nt create object Syntax for pure abstract class is abstract class x { public void abstract y(); public void abstract z(); public void abc() { }


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 abstract class is class which has a abstract method which means a method does not its own body.


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.


An Abstract method is one that has only a method declaration and no method definition. Similarly an abstract class is one that has one or more abstract methods. You can declare an abstract class or methods by using the keyword abstract in the class definition. Ex: public abstract class TestAbsClass { abstract void method1(); } Any class that extends this abstract class must provide implementation to the method "method1" or else it would have to be abstract as well.


A constructor of a class in invoked when a object of that class is created. As an abstract class can't have an object, so we can't create a constructor of the abstract class. But we can create a constructor of a concrete subclass of that abstract class and we have to pass the object of that concrete subclass to the abstract class.


An abstract class cannot have a constructor and hence you cannot invoke the constructor of the class - i.e., you can instantiate an abstract class and hence you cannot call the constructor of an abstract class.


Abstract classes are those classes that cannot be instantiated. Those classes are not fully implemented. Abstract class is base class for the family of child classes. It may contain some basic features but for some features only signature are given, the body of those methods must be written after inheriting this abstract class. Only if child implements all of the abstract methods it might be used (instantiated), otherwise child class is abstract too. To summarize it, you cannot instantiate class that is partial (missing all/some implementation).


abstract is keyword this is used for define abstract methods and abstract classes.abstract method means if you want define a method with out any body at that time you should define a method with abstract keyword. EX:public abstract int add() { } if you want define a class with abstract method must and should you define a class will be abstract class. Abstract EX:abstract class abc { abstract methods ------------ non abstract methods ---------------- } you can define abstract as well as non abstract methods in abstract class. in normal class you can define only normal methods only. you can't acess the methods which are in the abstract class from the same clss.by child class only you can acess the methods which are in abstract class. if you want to inherit abstract class must and should you have to define abstract methods which are in abstract class. Interface ----------:- interface is also like a clss.in interface you have to define only abstract methods only.you can't define normal methods in interface. EX: interface abc { abstract methods } by inharitance only you can acess the methods what are in the interface through the class.


No. The whole point of an abstract class is that it can not be instantiated.


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)


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).


public abstract class class_namne{ public abstract void method() {} }


False. In fact, it is possible to have no abstract methods in an abstract class.


1>Abstract class is use to extends the only one class not more then one class 2>Abstract class can contant construct 2>Abstract class can contant static block and non-static block both


An abstract in java is used to specify that the class/function is not yet complete. When a class in declared as abstract it means that it is not meant to be instantiated (you can't create variables of that type). This is because they are meant to be more of a guideline for other classes. When a class extends an abstract class it must either define all of the abstract methods from the abstract class or it must also be declared as an abstract class itself.


Abstract keywordused for method declaration declares the methods without implementations. Abstract class in java have abstract methods that is not implemented in abstract class, but implemented in subclasses in java program. If the class in java program is not required to get instantiated than that class use the abstract keyword but this class rather is available for other classes to extend by other classes. Abstract keyword will be used in method declaration to declare that method without providing the implementation in that java program. In other words we can say that, it formally unfinished class as well as method, that marked with the help of keyword abstract. Defining abstract is a way of preventing someone from instantiating a class that is supposed to be extended first. In java program abstract class is deliberately missing similar to like an interface which will missing all method bodies in the program. Abstract class provides a way to extend an actual class. We will not use new on abstract classes but will use abstract references in the java program, that always point to objects of the class that extends an abstract class. In java program for practical use of an abstract class, we will define a non-abstract class that extends an abstract one. This will use any of the inherited non-abstract methods. Most of the time abstract class may extend another abstract class. In that condition it need not implement all in the non-abstract methods. An abstract keyword used both on classes and methods. In case of class declared with an abstract keyword may not be instantiated that is the only thing that abstract keyword doing.