Sometimes we may come across a situation where we cannot provide
implementation to all the methods in a class. We want to leave the
implementation to a class that extends it. In such case we declare a class
as abstract.To make a class abstract we use key word abstract.
Any class that contains one or more abstract methods is declared as abstract.
If we don’t declare class as abstract which contains abstract methods we get
compile time error.
1)Abstract classes cannot be instantiated
2)An abstarct classes contains abstract method, concrete methods or both.
3)Any class which extends abstarct class must override all methods of abstract
class
4)An abstarct class can contain either 0 or more abstract method.
/*Abstract class:
A class which is declared as abstract is known as an abstract class.
It can have abstract and non-abstract methods. It needs to be extended
and its method implemented. It cannot be instantiated.
*/
// Example of abstract class
abstract class A{}
// Example of Abstract class that has an abstract method
abstract class Bike{
abstract void run();
}
class Honda4 extends Bike{
void run(){System.out.println("running safely");}
public static void main(String args[]){
Bike obj = new Honda4();
obj.run();
}
}
We cannot create objects of an abstract class. To implement features of an abstract class, we inherit subclasses from it and create objects of the subclass. A subclass must override all abstract methods of an abstract class. However, if the subclass is declared abstract, it's not mandatory to override abstract methods.
/**
* Simple Java program to prove that abstract class can have constructor in Java.
* @author http://java67.blogspot.com
*/
public class AbstractConstructorTest {
public static void main(String args[]) {
Server server = new Tomcat("Apache Tomcat");
server.start();
}
}
abstract class Server{
protected final String name;
public Server(String name){
this.name = name;
}
public abstract boolean start();
}
class Tomcat extends Server{
public Tomcat(String name){
super(name);
}
@Override
public boolean start() {
System.out.println( this.name + " started successfully");
return true;
}
}
Output:
Apache Tomcat started successfully
Sometimes we may come across a situation
where we cannot provide implementation to
all the methods in a class. We want to leave the
implementation to a class that extends it.
In that case we declare a class
as abstract by using abstract keyword on method
signature.In my framework I have created my
PageBase class as super
class of the all page classes.
I have collected all common elements
and functions into PageBase class and
all other page classes extent PageBase class.
By doing so, I don't have to locate very
common WebElements and it provides
reusability in my framework.
Also
1)Abstract classes cannot be instantiated
2)An abstarct classes contains abstract method,
concrete methods or both.
3)Any class which extends abstarct class must
override all methods of abstract class
4)An abstarct class can contain either
0 or more abstract method.
interface methods{
public void hey();
public void bye();
}
//unable to implement all the abstract methods in the interface so
// the other class automatically becomes abstract
abstract class other implements methods{
public void hey(){
System.out.println("Hey");
}
}
//able to implement all the methods so is not abstract
class scratch implements methods {
public void hey(){
System.out.println("Hey");
}
public void bye() {
System.out.println("Hey");
}
}
abstract class Language {
// method of abstract class
public void display() {
System.out.println("This is Java Programming");
}
}
class Main extends Language {
public static void main(String[] args) {
// create an object of Main
Main obj = new Main();
// access method of abstract class
// using object of Main class
obj.display();
}
}
Abstract classes have some special features:
it's impossible to create an instance of an abstract class;
an abstract class can contain abstract methods that must be implemented in non-abstract subclasses;
it can contain fields and non-abstract methods (including static);
an abstract class can extend another class, including abstract;
it can contain a constructor.
Sometimes we may come across a situation
where we cannot provide implementation to
all the methods in a class. We want to leave the
implementation to a class that extends it.
In that case we declare a class
as abstract by using abstract keyword on method
signature.In my framework I have created my
PageBase class as super
class of the all page classes.
I have collected all common elements
and functions into PageBase class and
all other page classes extent PageBase class.
By doing so, I don't have to locate very
common WebElements and it provides
reusability in my framework.
i)List<String> webs=driver.getWindowHandles();
=>create a list first to store web URLs in list
ii)findElements evaluates multiple elements so therefore will assigned to List <WebElement>
iii)To handle dynamic elements store it in the list and identify by index:
List<WebElement> all=driver.findElements(By.tagname(“”)); (or other locators).
Also
1)Abstract classes cannot be instantiated
2)An abstarct classes contains abstract method,
concrete methods or both.
3)Any class which extends abstarct class must
override all methods of abstract class
4)An abstarct class can contain either
0 or more abstract method.
// create an abstract class
abstract class Language {
// fields and methods
}
...
// try to create an object Language
// throws an error
Language obj = new Language();