Core Java for Selenium

Quality Assurance /
Software Testing Training
Core Java for Selenium

Classification: Restricted
Agenda
• Java Fundamentals
• Introduction to Java
• Programming Language fundamentals
• Key Java Concepts
• Strings and collections

1. Java Fundamentals
i. History of Java
ii. Features of java
iii. Introduction to OOPs

i. History of Java
• Background: Electronic Consumer Device
• Sun Commissioned ‘Project Green’
• Developed language ‘Oak-Later renamed to Java’
• Invented by Dr.James A.Gosling and his team in 1994
• Was dismissed as just another OO programming language
• Became popular with the rising popularity of ‘www’

ii. Features of Java
• Simple
• Robust
• Distributed
• Secure
• Portable
• Interpreted
• Multithreaded
• Portable
• Object Oriented

Simple
• Java designed as closely to C++ as possible
• Omits many confusing and rarely used features :
No header files
Structures
Unions
Pointers
Operator overloading
Virtual base class etc..

Robust
• Java Programs are reliable
• Early checking for potential problems
• Dynamic checking to eliminate error-prone situations.
• Developer doesn’t have to worry about
Bad Pointers
Memory Allocation Errors
Memory Leakage

Distributed
• An application when divided into smaller units is called as distributed
system
• Extensive library support protocols like TCP/IP, HTTP & FTP
• Applications can access objects across the net with ease.
Creating socket connections
Servlets
CGI Scripting
RMI enables communication between different objects

Platform Independence
.java file Intermediate
language code
abc.java abc.class
• Java compiler generates byte code
Platform independent
Bytecode code is an architecture-neutral file format to transport code efficiently
independent of hardware and Operating systems
The use of the same bytecode for all JVMs on all platforms
Allows Java to be described as a “compile once, run everywhere”
programming language
Source
Code
Compile
Byte
Code
Window
Linux
Mac

Secure
• Java applications used in distributed environments require emphasis on
memory
Security Manager
Allows applications to implement a security policy before
performing a possible unsafe or sensitive operation.
ByteCode Verifier
ByteCode Verifier is responsible for verifying the byte codes.
ByteCode do not violate Java’s security restrictions.

Portable
• Behavior of java basic types & arithmetic operators is consistent
• Java programs’s behavior is same on every platform – no data type
incompatibilities across platforms.
 int is always a 32-bit int
Strings stored in standard Unicode format

Interpreted
• ByteCode can be executed on any machine that has java interpreter and
java run time system
• Classes are linked only on need basis
• Java is both compiled and interpreted

iii) Object Oriented Approach
• Key concepts of object oriented programming are
• Abstraction
• Encapsulation
• Inheritance
• Polymorphism

Abstraction
• Abstraction is the process of identifying the key aspects of an entity and
ignoring the rest
• Only those aspects are selected that are important to the current problem
scenario
• Eg) Abstraction of a person object
• Enumerate attributes of a “person object” that needs to be created for
developing a database
• Useful for social survey
• Useful for health care industry
• Useful for payroll system

Abstraction of a Person Object
Social Survey Health Care Payroll System
Name Name Name
Age Age Age
Marital status -- --
Religion -- --
Income group -- --
Address Address Address
Occupation occupation Occupation
-- Blood group --
-- Weight --
-- Previous record --
-- -- Basic salary
-- -- Department
-- -- Qualification

Abstraction :Process of identifying the key aspects of an entity & ignoring the
rest
Encapsulation: Ensures that data within an object is protected and accessed
only by its methods

Encapsulation
• Encapsulation is a mechanism used to hide the data, internal structure and
implementation details of an object
• All interaction with the object is through the public interface of operations
• The user knows only about the interface, any changes to the
implementation does not affect the user
Methods
Variables

What is an Object?
• An entity is an entity which has a well defined structure and behaviour.
An object possesses certain characteristics as:
• State
• Behavior
• Identity

State of an Object
• The state of an object includes the current values of all its attributes.
• An attribute can be static or dynamic
• Employee Attributes
empid
name static
gender
Age
Address
Phone
Basicsal dynamic
Education
experience

Behavior of the Object
• Behavior is how an object acts and reacts, in terms of its changes and
message passing
Employee as an object
calculateSalary
printDetails Employee
Totality of operations – how an employee behaves or
responds to, is the behavior of the person.

Identity of an Object
• Identity is that property of an object which distinguishes it from all other
objects
• A single or a group of attributes can be an identity of an object
Employee
empId
Name
Gender
Phone
Age
Address
Phone
Basicsal
Education
empId uniquely
identifies a person
among others

Person as an Object
Attributes State Identity Behavior
empID empId = 10 empId = 10 Swipe Card
Name Name =
“Dhruv”
Fill TimeSheet
Gender Gender =
“male”
Wear Icard
Age Age=27 Calculate
Salary
Address Address =
“pune”
Print details
Phone Phone =
2342432
basicSalary basicSalary=80
00
Education
experience

Inheritance
• Classification helps in handling complexity
• Inheritance is the process by which one object acquire the properties of
another object
• “is a ”kind of hierarchy
Person
Employee
Wage
Employee Manager
Sales Person

Inheritance
• Generalization
Factoring out common elements within a set of categories into a more
general category called super class.
Requires good skill of abstraction
• Specialization
Allows to capture specific features of a set of objects.
Requires a depth of knowledge of domain.

Polymorphism
• The ability of different types of related objects to respond to the same
message in their own ways is called polymorphism
• Polymorphism helps to design extensible software, as new objects can be
added to the design without rewriting existing procedures

Polymorphism: same method having different implementations
• Compile/ static polymorphism – by function overloading
• Run time polymorphism – by function overriding

2. Introduction to Java
i. Compilation & execution of Java Program
ii. JDK, JVM & JRE
iii. Class & Object
iv. Access Modifiers
v. Data type
vi. Java class syntax

i) Compilation & Execution of Java Program
.java file
Java Class libraries
JDK
JRE
Source
code
compiler Byte
code
Class
loader
ByteCode verifier
Interpreter
Native OS
JVM
awt net rmii/o

ii) JDK, JVM and JRE
• JDK (Java Development Kit)
Comes along with standard class libraries and JVM embedded in it.
Contains software development tools such as a compiler or a debugger
which are used to compile and run the Java program.
• JRE(Java Runtime Environment)
It is an implementation of JVM, which actually executes the Java program
JRE provides some standard libraries and the JVM which can be used to
execute the java program
• JVM(Java Virtual Machine)
• JVM loads the appropriate class files for execution the java program and
then execute it
• JVM is a :
- Abstract specification
- A concrete implementation or
- A runtime instance

iii) Anatomy of JAVA class
• The term ‘class’ comes from the word called ‘classification’
• A class is a template for creation of like objects
• An object is an instance of class
• Classes are used to map real world entities into data members and member
functions
• By writing a class and creating objects of the class one can map two key
concepts of major pillars of object msodel i.e. Abstraction and
Encapsulation

Class: A class is a template for the creation of like objects

iv) Access Modifiers
• Access modifiers allow to specify the scope of the class members. We use
access modifiers to define the access control for classes, methods and
variables
• Access modifiers are of 4 types:
private – is accessible only within class
default – if we don’t specify any modifier then it is treated as default, this
can be accessible only within package
protected – is accessible within package , outside of the package but
through inheritance only
public – is accessible anywhere
• Non Access Modifiers
Static
Final : more like constant in C

Modifier Within
Class
Within
Package
Outside of
Package
(By Sub
Class)
Outside of
Package
Private Y N N N
default Y Y N N
protected Y Y Y N
public Y Y Y Y

v) Data Types : Is the classification of the type of data that variable can hold
in computer programming
Primitive Data Type
Boolean
Type
Numeric
Type
boolean
Integral
Type
Floating
Point Type
float double
Characte
r Type
Integer
Type
char longbyte short int

vi) Java Class Syntax
By Convention:
class Class_Name class name starts with capital case
{ e.g. class MySample
variable_Declaration;
variable(attribute or property)
method_Declaration() { name starts with small case
….. e.g. int date
…..
}
public static void main(String args[]) Method(behavior) name starts with
{ first word small case then next
…. Words 1st letter capital case called
…. Camel case
} //end of class e.g. void printDate() {
}

First Java Class
/* This is a comment */
//This is another comment
class MyDate
{ private int day, month, year; //variable
public void initDate() //method 1
{
day = 30;
month = 6;
year =2011;
}
public void printDate() //method 2
{
System.out.println(“Date is:” + day +”/” + month +”/” +year);
}

Create an Object
//continuation
public static void main(String args[])
{
MyDate d = new MyDate();
//method invocation
d.initDate();
d.printDate();
}
}

3. Language Fundamentals
i. Operators in Java
ii. Conditional & Loop statements
iii. Arrays in Java
iv. Exception handling
v. File handling

i) Operators
• Arithmetic operators
Addition, Subtraction, Multiplication, Division, Modulus, Increment,
Decrement
• Relational operators
== , != , > , >= , < , <=
• Logical operators
Logical Not Operator !
Logical AND Operator &&
Logical OR Operator ||
• Assignment operators
=

ii) Java Conditional & Loop statements
• Single Conditional statements
if(a>b) {
..
}
• Compound Conditional statements
If((a>b) && (a<c)) {
..
}
• Nested Conditions
if(a<b) {
if(a<c) {
if(a>b) {
}
}
}
• Java Switch statement : executes one statement from multiple conditions.

Loop Statements
• Loop statements are used to iterate a part of the program several times.
• Three types of loops
For loop
for(initialization ; condition ;incr / decr){
//code to be executed
}
While loop
while(condition){
}
Do.. While loop
do{
}while(condition);

Break, Continue & Comments
• Break statement
The Java break is used to break loop or switch statement. It breaks the
current flow of the program at specified condition. In case of inner loop, it
breaks only inner loop.
• Continue statement
The Java continue statement is used to continue loop. It continues the
current flow of the program and skips the remaining code at specified
condition. In case of inner loop, it continues only inner loop.
Comments in Java:
The java comments are statements that are not executed by the compiler
and interpreter. The comments can be used to provide information or
explanation about the variable, method, class or any statement. It can also
be used to hide program code for specific time.

iii) Arrays in Java
Normally, array is a collection of similar type of elements that have
contiguous memory location. Java array is an object the contains elements
of similar data type
• Advantage:
Code Optimization
Random access
• Disadvantage:
Size limit
Types of Array:
• Single dimensional
• Multi dimensional

iv. Exception Handling
• There is no perfect world
• Errors are inevitable
• Errors are shipped even with the best software
• Occur due to
Wrong input
Error on platform or system not configured
Program bugs
• Occur when the software is operational

Types of Errors
• Logical Errors
Counter not incremented in the while loop
Wrong expression written, resulting in incorrect output
• Run time Errors
Division by Zero
Array out of bounds
Dynamic memory allocation failed
File not found
File is corrupt

v) File Handling in Java
• High level operations/External operation
Create a folder
Delete a folder
Create a text file
Delete a text file
• Low level operations/ Internal operation
Read data from a file
Write data to a file

4. Key Java Concepts
i. Constructor
ii. Method overloading
iii. Method overriding
iv. Abstract Class
v. Interface

i) Constructor
• A constructor is used to initialize a newly created object
• It is implicitly invoked just after the memory is allocated for the object
using ‘new’ keyword
• It is a special method with same name as it’s class name
• No return type for constructor. Not even void
• A constructor without input parameter is default constructor
• Constructor can be overloaded

ii) Method Overloading
• Reusing the same name for method
• The method calls are resolved at compile time using
method signature.
• Compile time error occurs if compiler cannot match the arguments or if
more than one match is possible
• Method signature consists of
Number of arguments passed to a function
Data types of arguments
Sequence in which they are passed

Sample Program
class MathEngine
{
public int add(int num1, int num2)
{
….
}
public int add(int num1, int num2, int num3)
{
…
}
}
class Program
{
public static void main(String args[])
{
MathEngine obj = new MathEngine();
int result = obj.add(12,13);
int output = obj.add(15,16,17);
}
}

iii) Method Overriding
• Polymorphism is achieved using overriding functions using inheritance
• It gives ability to define a behavior that’s specific to the sub class type
based on its requirements
• The version of a method that is executed will be determined by the object
that is used to invoke a method
Parent object ---- > parent method
Child object ----- > child method

vi) Concrete and Abstract Class
• Concrete class
A class which describes the functionality of an object
It can be instantiated
• Abstract class
A class which contains generic non implemented methods.
Descendant classes comes up with the implementation for those methods in
their own ways
It can contain abstract as well as non abstract methods
Abstract methods do not have implementation
Implementation is left to the inheriting sub classes
Cannot be instantiated

v) Interface
• An interface defines a contract between a provider and a consumer.
• Enables common design even across those classes not in hierarchy
• Defines a standard set of properties, methods and events.
• Any class implementing an interface has to provide the functionality
Interface
(Some
common
design)
Provider
class
Consumer
class
Implemented
by
Used
by
contract

Features of an Interface
• Interface is essentially a collection of constants and abstract methods
• The interface approach is sometimes known as “programming by contract”
• Data members in an interface are always public, static and final
• A sub class can only have a single superclass in java but a class can
implement any number of interfaces
• If a class implements an interface then have to implement all the methods
of it.

6. Strings And Collections
i. String Class – StringBuffer & StringBuilder
ii. Generics & collection

String class
• Java library contains a predefined class called as String.
• The String type is not a primitive type.
• But in certain cases Java treats it like one
• The ability to declare String literals instead of using new to instantiate a
copy of the class
String s = “seed”
• String is the “First class object”

String Class
• String class represents an “immutable” string.
• ie. Once an instance is created, the string it contains can not be changed.
• To change the String referenced by a string variable, you throw away the
old string and replace it with the modified one.
“Bye”
“Hello”
New String
Old
String

StringBuffer Class
• StringBuffer class allows to create “mutable” strings
• It reallocates memory of a given length to accommodate changes within a
same object
• StringBuffer is thread safe
• The buffer grows automatically as characters are added.
Eg StringBuffer sb = new StringBuffer();

StringBuilder Class
• StringBuilder is introduced in Java 5.0 version.
• This is just an alternative to StringBuffer class.
• There is no difference between StringBuffer and StringBuilder
• Methods of StringBuilder class are not thread safe
• Recommended for faster applications.

Why collections?
• Array size is fixed. Size cannot be increased dynamically.
• In actual development scenario, same type of objects need to be
processed.
• Data is obtained from data source like files or database.

Collection – Interface hierarchy Java7
Collection
List Queue Set Map
Deque
Navigable
Set
SortedSet
NavigableMap
SortedMap
Iterator

Collection Interfaces
• Allow collections to support a different browser
Interface Description
List Represents a collection of objects
that is accessed by an index. An
ordered collection
Set Represents a collection that contains
no duplicate elements. An order is
not fixed
Map Represents a collection of key- value
pairs
Queue Represents a collection designed for
holding elements prior to processing
Iterator Supports a simple iteration over
collection
Comparator Comparison function which imposes
a total ordering on some collection
of objects

List Interface
• Ordered Collection
• May contain duplicates
• Implemented by classes
-- ArrayList [Resizable – array implementation of the List interface]
-- LinkedList [Doubly linked list implementation of the list]
--Vector [the Vector class implements a growable array of objects]

Set Interface
• Collection of unique elements
• No duplicate elements allowed
• Collection not in any particular order (random)
• Implemented by the Hashset

Thank You

Core Java for Selenium

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