Abstract class may or may not contain abstract methods and it can't be instantiated. Even a class which is having all concrete methods can be declared as abstract class by using abstract keyword the main intention is to not instantiate the class only. Abstract method always doesn't have definition of the method it will have … Read more

Marker interface plays vital role even though it doesn't contain any methods.The main purpose is to identify the special objects from normal objects for example if you want to serialize an object then how you will inform to the JVM to serialize the particular object because there may be so many objects available in JVM. … Read more

Generally by making a constructor as private one can't instantiate the class by creating objects.The following classes generally will have private constructors they are abstract classes and singleton classes.

To execute Java file from command use the following syntax c:/>java filename without extension