Java Quick Tutorial

Java for Selenium

1) Java Environment Setup & Verify

2) Comments in Java

3) Java Data Types

4) Java Modifiers

5) Variables

6) Operators

7) Conditional Statements

8) Loop Statements

9) String Handling in Java

10) Arrays in Java

11) Java IO Operations and File Handling

12) Java Built-in Methods

13) Java User defined Methods

14) Java Exception Handling

15) Java OOPS (Object Oriented Programming System)
a) Inheritance
b) Polymorphism
c) Abstraction
d) Encapsulation

Java Quick Tutorial
Java Step by Step Tutorial

1) Java Environment Setup & Verify

Steps:

Download Eclipse IDE and extract
Download Java and Install
Launch Eclipse IDE
Create Java Project
Create Java Package
Create Java Class
Write Java Program and Execute

2) Comments in Java

Purpose of Comments in Computer Programming

To make the Code Readable
To make the Code disable from Execution.

Java supports Single line comment and multiple line comments.

Single line Comment- // before the Statement

Multiple lines comment/comment a block of statements

/* Statements

———————–

——————–

———-*/

Example:
public static void main(String[] args) {
//It is a Sample Java Program
int a=10, b =20;
System.out.println(a+b);

/if ( a > b){ System.out.println(“A is a Big Number”); } else { System.out.println(“B is a Big Number”); }/

}
}

3) Data Types in Java

A Data Type is a classification of the type of data that a variable or object can hold in computer programming.

Example for General Data Types:

Character,

Integer,

String

Float

Boolean etc…

Java supports two categories of Data types.

a) Primitive Data Types

b) Reference Data Types.

Example:

int a=10;
char b =’A’;
double c = 123.234;
boolean d = true;
System.out.println(a);
System.out.println(b);
System.out.println(c);
System.out.println(d);

4) Java Modifiers

Modifiers are used to set access levels for Classes, Variables and Methods etc…

Two types of Modifiers in Java

1) Access Modifiers (default, public, private and protected)

2) Non Access Modifiers (static, final, abstract, synchronized etc…)

Example:
public class Class1 {
public int a =10, b =20;
public void add(){
int result = a +b;
System.out.println(result);
}
public static void main(String[] args) {
Class1 obj = new Class1();
obj.add();
}
}

5) Variables in Java

A named memory location to store temporary data within a program.

Three types of variables in Java

1) Local Variables

2) Instance Variables

3) Class / Static Variables

Example:

public class Class1 {
public static int a =100, b =20;

public static void main(String[] args) {
int c = 30;
System.out.println(a);
System.out.println(c);

if (a > b){
int d=40;
System.out.println(a + b + d);
System.out.println(d);
}
//System.out.println(d);
System.out.println(b);
}
}

6) Operators in Java

Operators are used to perform Mathematical, Comparison and Logical Operations.

Categories of Operators in Java

1) Arithmetic Operators

2) Relational Operators

3) Assignment Operators

4) Logical Operators
Etc…

1) Arithmetic Operators

a) Addition + (Addition, String Concatenation)

b) Subtraction – (Subtraction, Negation)

c) Multiplication *

d) Division /

e) Modules %

f) Increment ++

g) Decrement —

2) Relational Operators

a) ==

b) !=

c) >

d) >=

e) <

f) <=

3) Assignment Operators

a) Assignment =

b) Add and Assign +=

c) Subtract and Assign -=

d) Multiply and Assign *=

4) Logical Operators

a) Logical Not operator !

b) Logical And Operator &&

c) Logical Or operator ||

Example:

public class Class1 {
public static void main(String[] args) {
int a=10, b=20, c =30;

System.out.println(a+b);
System.out.println(a*b);
System.out.println(a-b);

System.out.println(a > b);
System.out.println(a < b);

System.out.println(a+10);

if ((c > a) && (c > b)){
System.out.println(“C is a Big Number”);
}
else {
System.out.println(“C is Not a Big Number”);
}

}
}

7) Java Conditional Statements

1) Two types of statements

a) if statement

b) switch statement

2) Three types of Conditions

a) Single Condition (Positive/Negative)

b) Compound Condition (Positive/Negative)

c) Nested Condition (Positive/Negative)

3) Usage of Conditional Statements

a) Execute a block of statements when a condition is true.

b) Execute a block of statements when a condition is true, otherwise execute another block of statements.

c) Execute a block of statements when a Compound condition is true, otherwise execute another block of statements.

d) Decide among several alternates (Else if)

e) Execute a block of statements when more than one condition is true (Nested if).

f) Decide among several alternates using Switch statement

Example:

int a=100, b=20;

if (a > b){
System.out.println(“A is a Big Number”);
}

if (a > b){
System.out.println(“A is a Big Number”);
}
else {
System.out.println(“B is a Big Number”);
}

if (!(b > a)){
System.out.println(“A is a Big Number”);
}
else
{
System.out.println(“B is a Big Number”);
}

8) Loop Statements

Used for Repetitive execution.

Four types of loop structures in Java

1) for loop

2) while loop

3) do while loop

4) Enhanced for loop(Arrays)

Examples:

//Print 1 to 10 Numbers
for (int i=1; i<=10; i++){
System.out.println(i);
}

//Print 1 to 10 Numbers
int i=1;
while (i<=10){
System.out.println(i);
i++;
}

//Print 1 to 5 Numbers Except 4
for (int i = 1; i <=5; i++){
if (i != 4){
System.out.println(i);
}
}

9) String handling in Java

Sequence of characters written “”

String may contain Alfa bytes or Alfa-numeric or Alfa-numeric and Special characters or only numeric.

“ABCD”
“India123”
“India123$#@”
“123”

Example:
System.out.println(“India”);
System.out.println(“India123”);
System.out.println(“123”);
System.out.println(“$%^”);
System.out.println(“India123%^&*”);

Creating Strings

String myTool = “UFT”;//String Variable
String [] myTools ={“UFT”, “RFT”, “Selenium”};//Array of Strings
System.out.println(myTool);//UFT

Example 3:

String str1 =”Selenium”;
String str2 = ” UFT”;
System.out.println(str1 + str2);//Selenium UFT
System.out.println(str1.concat(str2));//Selenium UFT
System.out.println(“Selenium”+1+1);//Selenium11
System.out.println(1+1+”Selenium”);//2Selenium

10) Arrays in Java

Generally, Array is a collection of similar type of elements.

In Java, Array is an Object that contains elements of similar data type.

Each item in an Array is called an Element.

Example:

int a [];
a= new int[3];
a[0]=10;
a[1]=20;
a[2]=30;
System.out.println(a[1] + a[2]);

int a [] = new int [3];
a[0]=10;
a[1]=20;
a[2]=3;
System.out.println(a[0] – a[2]);

int a [] = {10, 20, 30, 40};
System.out.println(a[1] + a[3]);

//Different Types of Arrays

char [] a = {‘A’, ‘B’, ‘C’, ‘d’};//Array of Characters
int [] b ={10, 20, 30, 40}; //Array of Integers
String [] c = {“UFT”, “RFT”, “Selenium”};//Array of Strings
boolean [] d ={true, false, false, true}; //Array of Boolean values.
double [] e ={1.234, 2.345, 5.6}; // Array of decimal point values

11) Java IO Operations

Reading Data (Read Input, Read data from files)

Using java.util.Scanner is the easier way and it includes many methods to check input is valid to read.

Examples:

1) Read Input:

Scanner scan = new Scanner(System.in); //System.in is an Input stream
System.out.println(“Enter Your Name”);
String name = scan.nextLine();
System.out.println(“Your Name is “+ name);

System.out.println(“Enter Your Number”);
int num = scan.nextInt();
System.out.println(“Your Number is “+ num);

2) Display Output on the Console

public static void main(String[] args) {
int a =10, b=20;
System.out.println(a);//10
System.out.println(“welcome to Selenium”);//welcome to Selenium
System.out.println(“Addition of a, b is “+ (a+b));//Addition of a, b is 30
System.out.println(“value of a is “+ a + ” Value of b is “+b);//Value of a is 10 value of b is 20”
}

12) File Handling

Using File Class we can handle Computer files.

Example:

1) Create a Folder

File fileObject = new File(“C:/Users/gcreddy/Desktop/ABC”);
fileObject.mkdir();

13) Java Methods

A Java Method is a set of statements that are grouped together to perform an operation.

Methods are also known as Functions.

In structured programming (Ex: C Language) we use Functions (Built-in and User defined)

In Object Oriented Programming (Ex: Java Language) we use Methods (Built-in and User defined)

i) When we choose Methods?

Whenever we want perform any operation multiple times then we choose methods.

Advantages of Methods

Code Reusability, using methods we can reduce the project code size.

Code Maintenance is easy.

ii) Types Methods in Java

Two types of Methods

1) Built in /Pre-defined Methods

2) User defined Methods

equals() Method

Compares two strings and supports 2-way comparison

Example:

public static void main(String[] args) {
String str1 = “selenium”;
String str2 =”SELENIUM”;
String str3 =”seleniuma”;
String str4 = “selenium”;

System.out.println(str1.equals(str2));//false
System.out.println(str1.equals(str4));//true

round()
Rounds the value to nearest integer.

public static void main(String[] args) {
double a =10.234;
double b =-10.784;

System.out.println(Math.round(a));//10
System.out.println(Math.round(b));//-11
}

isAlphabetic()

Checks weather the value is alfa byte or not?

public static void main(String[] args) {
char a =’Z’;
char b =’1′;

System.out.println(Character.isAlphabetic(a));//true
System.out.println(Character.isAlphabetic(b));//false
System.out.println(Character.isAlphabetic(‘B’));//true
System.out.println(Character.isAlphabetic(‘a’));//true
System.out.println(Character.isAlphabetic(‘*’));//false

14) User Defined methods in Java

Two types of user defined methods

1) Method without returning any value
a) Calling Methods by invoking Object
b) Calling methods without invoking Object

2) Method with returning a Value
a) Calling Methods by invoking Object
b) Calling methods without invoking Object

Calling External Methods

Examples:

//User defined methods
public int multiply(int a, int b, int c){
int result = abc;
return result;
}
public static void main(String[] args) {
//Create Object
JavaMethods abc = new JavaMethods();

//Call methods
int x = abc.multiply(10, 25, 35);
System.out.println(x);

//Create a method without returning any value
public static void studentRank(int marks){
if (marks >= 600){
System.out.println(“Rank A”);
}
else if (marks >=500){
System.out.println(“Rank B”);
}
else{
System.out.println(“Rank C”);
}
}

public static void main(String[] args) {
//Call Methods
JavaMethods.studentRank(650);
}

15) Java Exception Handling

An Exception is an event that occurs during execution of a program when normal execution of a program
is interrupted.

Exception handling is a mechanism to handle exceptions.

Common Scenarios where exceptions may occur

1) Scenario where ArithemeticException occurs

2) Scenario where NullPointerException occurs.

3) Scenario where NumberFormatException occurs

4) Scenario where ArrayIndexOutofBounds exception occurs

Example:

public static void main(String[] args) {
int a =10;
int b =0;
int result = a/b;
System.out.println(result);
System.out.println(“Hello Java”);
System.out.println(“Hello Selenium”);
}

16) Java Object Oriented Programming

Four fundamentals of OOPS:

a) Inheritance

b) Polymorphism

c) Abstraction

d) Encapsulation

a) Inheritance

It is a process of Inheriting (reusing) the class members (Variables and Methods) from one class to another.

Non static class members only can be inherited.

The Class where the class members are getting inherited is called as Super Class/parent Class/Base Class.

The Class to which the class members are getting inherited is called as Sub Class/Child Class/Derived Class.

The Inheritance between Super class and Sub class is achieved using “extends” keyword.

Example

Class 1:

public class ClassA {
int a =10;
int b =20;

public void add(){
System.out.println(a+b);
}
public static void main(String[] args) {
ClassA objA = new ClassA();
System.out.println(objA.a);//10
objA.add();//30
}
}

Class 2:

public class ClassB extends ClassA{
int a =100;
int b =200;

public void add(){
System.out.println(a+b);
}
public static void main(String[] args) {
ClassB objB = new ClassB();
System.out.println(objB.a);//100
objB.add();//300
}
}

b) Polymorphism

Existence of Object behavior in many forms

There two types of Polymorphism

1) Compile Time Polymorphism / Method Overloading

2) Run Time Polymorphism / Method Overriding

1) Compile Time Polymorphism / Method Overloading

If two or more methods with same name in the same class but they differ in following ways.

a) Number of Arguments

b) Type of Arguments

Example:

public class Class1 {
public void add(int a, int b){
System.out.println(a+b);
}

public void add(int a, int b, int c){
System.out.println(a+b+c);
}

public void add(double a, double b){
System.out.println(a+b);
}

public static void main(String[] args) {
Class1 obj = new Class1();
obj.add(1.23, 2.34);
obj.add(10, 20);
obj.add(1, 5, 9);
}
}

c) Abstraction

It is a process of hiding implementation details and showing only functionality to the user.

Two types of Methods in Java

1) Concrete Methods (The methods which are having body)

2) Abstract Methods (The methods which are not having body)

If we know the method name but don’t know the method functionality then we go for Abstract methods.

Java Class contains 100% concrete methods.

Abstract class contains one or more abstract methods.

Example for Abstract Class:

public abstract class Bikes {

public void handle(){
System.out.println(“Bikes have handle”);
}
public void seat(){
System.out.println(“Bikes have Seats”);
}

public abstract void engine();

public abstract void wheels();

public static void main(String[] args) {
//Bikes obj = new Bikes();

}
}

d) Encapsulation

It is a process of wrapping code and data into a single unit.

Ex: Capsule (mixer of several medicines)

Encapsulation is the technique making the fields in a class private and providing access via public methods.

It provides control over the data

By providing setter and getter methods we can make a class read only or write only.

Example:

Class 1:

public class Class1 {
private String name =”Test Automation”;

public String getName(){
return name;
}
public void setName(String newName){
name = newName;
}
public static void main(String[] args) {
Class1 obj = new Class1();
System.out.println(obj.getName());
}
}

Class 2:

public class Class2 extends Class1{

public static void main(String[] args) {
Class2 abc = new Class2();
//abc.setName(“Selenium Testing”);
System.out.println(abc.getName());
}

}


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