Classes and Objects
In java, all data and functions are declared in a class. To declare a class, keyword class is used. Keyword class is followed by class name. Class is a collection of objects that contains a set of data items (Properties) and related functions (Behaviours). Class is a way to bind the data describing an entity and its associated functions together. Class contains Instant variables, Constructors, and Member methods. Instance variables are generally used within the member methods of the class. The variables that are declared within class are called Instance variables. Each object of a class contains these variables. These are used in the member function.
A constructor in a class is a special type of method called at the creation of an object. It is called a constructor because it constructs the values of data members of the class. They have same name as a class without any access modifier. Member methods deal with instant variables. Member methods are the methods inside the class. These methods deal with instance variables. Member methods are common to all the objects. Objects are created using the new operator along with the class constructor. It allocates memory and returns the reference to the newly created object. An object is an instance of a class which is used to invoke class elements such as methods. Through objects’ interaction, a program can carry out various tasks. Once a class is declared, its variable is created, which is known as an object.