Object in Java..

        

Object is a thing used to access a member in class. (i.e) the class members which are non static can be accessed in other class using object it is also referred as Instance of a Class. It is created during run time so its a run-time entity. Object can be used access only one class. But class can have multiple objects unless the constructor is declared as static. For static constructor only one object can be created. During run time object gets created and only when object created the memory of the class variables gets created and the object's memory gets stored in heap. Object can't be created for abstract class and interfaces.

  Any object should posses 

• Identity
• State
• Behavior 

To create a object

1. Declare a reference variable
2. Construct object with "new" keyword. new is used for dynamic memory allocation.
3.  Assign the reference variable to new keyword. and construct the object.

Example:

1. class A{
2. int a,b;
3. static int x,y;
4. A(){
5. }
6. void xy(){
7. }
8. }
9.  class B{
10. void main(){
11. A obj = new A();
12. obj.xy();
13. }
14. }

 in this example, the class A has 2 non-static variables, 2 static variables and 1 constructor 1 method,
the new A() (line 11) is called as object which refers to class A. the obj (line 11) is called as reference variable of class A. when obj is created then the space for a,b (line 2) gets created in heap, for remaining variables and methods its created in class memory. as the same time the constructor of class A gets called. If its not present the java creates a empty constructor.


I hope the concept of object is understood if any queries comment below and stay tuned for more blogs.....

Quiz to solve : Find objects and class in this picture ?  (post your answers as your comments)

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