abstract class in java
Sometimes we may come across a situation where we cannot provide implementation to all the methods in a class. We want to leave the implementation to a class that extends it. In such case we declare a class as abstract.To make a class abstract we use key word abstract. Any class that contains one or more abstract methods is declared as abstract. If we don’t declare class as abstract which contains abstract methods we get compile time error. 1)Abstract classes cannot be instantiated 2)An abstarct classes contains abstract method, concrete methods or both. 3)Any class which extends abstarct class must override all methods of abstract class 4)An abstarct class can contain either 0 or more abstract method.