Modifiers and Interfaces (Selenium 4

Modifiers

public Access Modifier

Classes/variables/methods specified with ‘public’ access modifier can be accessed directly by the classes which are in the same package – Demonstrate
Classes/variables/methods specified with ‘public’ access modifier can be accessed by the classes outside the package after importing the classes – Demonstrate

private Access Modifier

Java classes cannot be specified with ‘private’ access modifier – Demonstrate
variables/methods specified with ‘private’ access modifier can be accessed only with in the same class – Demonstrate

default Access Modifier

When no modified is specified before classes/variables/methods, then we name it as default modifier – Demonstrate
default means public to all the classes inside the same package and private to the classes which are outside the package – Demonstrate

protected Access Modifier

protected means public to all the classes inside the same package and private to all the classes which are outside the package except child classes
Java classes cannot be specified with ‘protected’ access modifier – Demonstrate
While accessing the protected variables/methods outside the packages using sub-classes, we don’t have to create an object to access them as they are inherited variables and methods – Demonstrate

static Non-Access Modifier

Java classes cannot be specified with ‘static’ non-access modifier – Demonstrate
Variables declared directly inside the class but outside the methods and are specified with ‘static’ modifier are known as static variables
Memory allocated to the static variables is different from the memory allocated to the instance variables
static variables needs to be accessed with the help of Class name, as they belong to the Class memory
static variables are generally used to store common data, where as Object variables/Instance variables are used to store Object specific data.
wheels variable can be used as a static variable/class level variable as it has common data i.e. wheels count is 4 for all the cars in the market
Where as cost variable cannot be used as a static variable as its value changes from car to car, hence we use it as an Object variable/Instance variable.
static can also be used with methods
static can only access static stuff
You have to create object to overcome this

final Non-Access Modifier

The value of the variable cannot be changed on specifying it with final non-access modifier
final modifier specified classes cannot be inherited/extended by other classes
final modifier specified methods in a class cannot be overridden by its sub-classes

abstract Non-Access Modifier

variables cannot be specified with ‘abstract’ non-access modifier – Demonstrate
On specifying a method with abstract modifier, we can just declare the method without implementing it
Classes having at-least one abstract specified method must be specified as abstract
Sub-Class inheriting the Super-Class needs to implement the abstract specified methods in Super-Class
Purpose of abstract methods – Used when the super-class dont have to implement everything, and when the sub-classes inheriting the super-class needs to implement them.
Objects cant be created for abstract classes, we have to create a Sub-Class and access its variables/methods using Sub-Class object reference

Interfaces

The purpose of an interface is to just to declare all the functionalities required before actually implementing them.

Interfaces looks similar to Classes and are extensions of abstract classes
Create an interface say ‘Bank’ in Eclipse IDE and create variables & methods inside it
Variables in the interfaces are of static and final type
In abstract classes, we can have both methods (i.e. implemented and non-implemented), where as in interfaces, we cannot implement any methods.
Classes use implements keyword to implement any interface
Classes implementing an interface can have their own specific methods apart from methods which are acquired from an interface
Objects cannot be created for an interface – Demonstrate
Object can be created for the Classes which are implementing the interfaces, for accessing interface defined methods and class specific methods – Demonstrate
Follow the below steps to provide the access the interface specific methods and not to access the class specific methods
Create an object for the Class which is implementing the interface
Assign the object of the class to the interface reference variable
Using the interface reference variables, we can now access only the methods which are declared in the interface

By,

Arun Motoori

Modifiers and Interfaces (Selenium 4 – Session 8)