What is Class in OOPS?


  • A class defines the properties and behavior (variables and methods) that is shared by all its objects. It is a blue print for the creation of objects.
  • Definition: Class is a way of binding the Data Members and Methods in a single unit.
  • Data Members of a class are also known as properties or attributes.
  • Methods of a class are also known as behaviors or accessories or functions.
  • In java, every program must be defined or developed with respect to class only i.e. No java program can be developed without the features of class.
  • In Object-Oriented Programming, we can have two types of methods. They are:

            (a) Member Methods  (b) Non-member Methods

  • Member Methods: A member method is one, which will come under the scope of a class.
  • Non-member Method: A non-member method is one, which will not come under the scope of a class.
  • Java does not allow non-member methods it allows only member-methods.
  • All the methods in java must be defined within the class only, i.e. Java Environment does not allow outside method definition.
  • Whenever we define a class, the data members of the class do not occupy the memory space. They occupy the memory space, when we create an object.
  • Syntax to define a User-defined Data type: Class



            Variable / Data member declaration

            Method definition



Class Student


            int rNo;

            void result();





  • A keyword “class” is used for creating/developing user-defined data type.
  • <class-name> represents a valid java variable name and it is treated as the name of the class. Class name is basically used to create objects.
  • Whenever, we create a class, no memory space is occupied for the data members of the class.
  • Class contains two parts:

            (a) Variable Declaration or the Data Members

            (b) Method Definition

  • Variables-declaration represent, what type of data members, we use as a part of the class.
  • Methods definitions represent what type of methods, we use as a part of the class to perform specific operations.
  • Every class must start with opening curly bracket ({) and terminates with closing curly bracket (}).
  • Whenever more than one class are in same file then compiler will create .class file for all the classes, but interpreter will execute only a class which have main method.

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