Dart: Private Instance Variable

For creating private Instance variable we have to use " _ " before variable name.
This kind of Instance exists in only library. No one can access this Library from outside.
- First we have to create one library for this we use " library " keyword.
  
  Then we create one class which is " class A ".
- In Class A we passed one variable called _privateInstanceVariable = 20.
- In class A we create on function call display and pass one print statement on this function we which we called in our other file .

  library private_instance_variable;

  class A 
  {
   var _privateInstanceVariable = 20;

    void display()
    {
      print("The Private Instance Variable value is : $_privateInstanceVariable ");
    }
  }

This file we called in our second file using import keyword , and then we extend class A on this file using extend keyword.
If we try to change value of obj B than we face error on this. because obj get value from class B where Class B get value from Class A from other file and this is private Instance variable so we can not change the value of obj.

import "136_Dart_Private_Instance_Variable.dart";


void main()
{
 var obj = B();
 obj.display();

}

class B extends A{}