- How do we declare an abstract class?
- Can abstract class have normal methods?
- Can an abstract class extend another abstract class?
- Can an abstract class have a parent class which is concrete?
- Can an abstract class may be final?
- Can we inherit abstract class?
- Can an abstract class extend concrete?
- What is difference between abstract class and interface?
- Can an abstract class be a subclass?
- What is abstract superclass?
- Can abstract class have constructors?
- What is the purpose of an abstract class?
How do we declare an abstract class?
To create an abstract class, just use the abstract keyword before the class keyword, in the class declaration.
You can observe that except abstract methods the Employee class is same as normal class in Java..
Can abstract class have normal methods?
It can have abstract methods(methods without body) as well as concrete methods (regular methods with body). A normal class(non-abstract class) cannot have abstract methods. … An abstract class can not be instantiated, which means you are not allowed to create an object of it.
Can an abstract class extend another abstract class?
An abstract class can extend another abstract class. And any concrete subclasses must ensure that all abstract methods are implemented. Abstract classes can themselves have concrete implementations of methods. These methods are inherited just like a method in a non-abstract class.
Can an abstract class have a parent class which is concrete?
We can declare an abstract class using the abstract keyword. It may have abstract as well as concrete (non-abstract) methods. An abstract class can have static methods. … A class derived from the abstract parent class must implement each method that is declared as abstract in the parent class.
Can an abstract class may be final?
An abstract class cannot be declared as final. Only abstract class can have abstract methods. A private, final, static method cannot be abstract, as it cannot be overridden in a subclass.
Can we inherit abstract class?
An abstract class defines the identity of a class. An interface can inherit multiple interfaces but cannot inherit a class. An abstract class can inherit a class and multiple interfaces. … An abstract class can declare constructors and destructors.
Can an abstract class extend concrete?
An abstract class always extends a concrete class ( java. lang. … If you want to instantiate it, you will have to subclass it with a concrete implementation of those abstract methods and instantiate it through the concrete class.
What is difference between abstract class and interface?
Abstract class can inherit another class using extends keyword and implement an interface. Interface can inherit only an inteface. Abstract class can be inherited using extends keyword. Interface can only be implemented using implements keyword.
Can an abstract class be a subclass?
Abstract classes cannot be instantiated, but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract .
What is abstract superclass?
Abstract Super Class. A common superclass for several subclasses. Factor up common behavior. Define the methods they all respond to. Methods that subclasses should implement are declared abstract.
Can abstract class have constructors?
Yes! Abstract classes can have constructors! Yes, when we define a class to be an Abstract Class it cannot be instantiated but that does not mean an Abstract class cannot have a constructor. Each abstract class must have a concrete subclass which will implement the abstract methods of that abstract class.
What is the purpose of an abstract class?
The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.