Classes and Objects in Java

Class

  • Class is the collection of similar type of objects which
    have some common properties.
  • Class is a concept which is implemented by object.
  • Class is a blueprint of java program from which we create
    object, then object is instance of class.
  • We can also say that class is a collection of variables and methods.
Class
{
         Methods: Represent Property
Variables: Represent
Behavior
}

Object

  • Any real world entity which have physical existence either
    living or non living is called an object.
  • It is a runtime memory area. Object goes to heap.
Classes and Objects in Java

How to Create an Object?

  • In Java object of any class is created using new keyword.
  • new keyword reserve the memory for an object in heap and
    generate an implicit reference id which is stored in a reference variable.
class Emp
{
                String name;
                int salary;
                void get(String n1,int s1)
                {
                                name=n1;
                                salary=s1;
                }
                void show()
                {
                                System.out.println(name);
                                System.out.println(salary);
                }
                public static void
main(String…s)
                {
                                Emp e1=new
Emp();
                                e1.get(“aa”,101);
                                e1.show();
                                new
Emp().get(“bb”,102);            //Anonymous
Object
                                new
Emp().show();                         //Anonymous
Object
                }
}


Note: Reference variables and local variables goes to stack and methods goes to method area

Output
Classes and Objects in Java Program

  • In above example total three objects are created. Firstly an
    object is created using new operator and its reference id is stored in
    reference variable e1. Then using e1 we call get() and show() methods. After
    that we are creating two anonymous objects. You can see that we are getting different
    outputs in three objects.
  • Anonymous object is an object without name.
  • We can store one reference id into more than one reference
    variable.
    Example: Emp e1=new Emp();
                   Emp e2=e1;
If you find anything wrong or missing in above tutorial then please mention it in comment section.

Leave a Reply

Your email address will not be published. Required fields are marked *