Unary | ++, -- | Increase or decrease by one |</div>

Example 1: Arithmetic operators

public class ArithmeticExample 
{   
 public static void main(String[] args)
 {       
 int a = 10;        
int b = 3;       
 System.out.println(a + b);
 // 13        System.out.println(a - b); 
// 7        System.out.println(a * b); 
// 30        System.out.println(a / b); 
// 3        System.out.println(a % b); 
// 1    }}

Example 2: Relational and logical operators

int age = 25;
boolean hasAccount = true;
System.out.println(age >= 18); 
// trueSystem.out.println(age < 18);
  // falseSystem.out.println(age >= 18 && hasAccount); 
// trueSystem.out.println(age < 18 || hasAccount); 
 // trueSystem.out.println(!hasAccount);            
 // false

• && means both conditions must be true.
• || means at least one condition must be true.
• ! reverses a boolean result.

Automation testing example

boolean usernameEntered = true;
boolean passwordEntered = true;
boolean loginButtonEnabled = true;
if (usernameEntered && passwordEntered && loginButtonEnabled)
 {    
System.out.println("Ready to test login");
}

6. Conditional statements — if, else, switch

A. if statement

int marks = 75;
if (marks >= 40)
 {    
System.out.println("Pass");
}

B. if-else statement

int marks = 35
if (marks >= 40)
 {   
System.out.println("Pass");
}
 else
 {    
System.out.println("Fail");
}

C. else-if ladder

int marks = 85;
if (marks >= 90) 
{   
 System.out.println("Grade A+");
}
 else if (marks >= 75) 
{ 
   System.out.println("Grade A");
}
 else if (marks >= 40) 
{  
  System.out.println("Grade B");
}
 else 
{    
System.out.println("Fail");
}

D. switch statement

String browser = "Chrome";switch (browser) {    
case "Chrome":       
 System.out.println("Launch Chrome");       
 break;    
case "Firefox":        
System.out.println("Launch Firefox");        
break;    
case "Edge":        
System.out.println("Launch Edge");       
 break;   
 default:       
 System.out.println("Unsupported browser");}

Automation testing example

String actualStatus = "PASS";if (actualStatus.equals("PASS")) 
{   
 System.out.println("Test completed successfully");
} 
else
 {    
System.out.println("Investigate test failure");}

• Use if-else for ranges, complex conditions, and boolean checks.
• Use switch for selecting among specific values, such as browser names or menu options.

7. Loops — for, while, do-while

A. for loop

public class ForLoopExample 
{    
public static void main(String[] args)
 {       
 for (int i = 1; i <= 5; i++)
 {           
 System.out.println("Test iteration: " + i);     
   }   
 }
}

Test iteration: 1Test iteration: 2Test iteration: 3Test iteration: 4Test iteration: 5

• int i = 1: Initialization.
• i <= 5: Condition.
• i++: Increment after each iteration.

B. while loop

int i = 1;while (i <= 3) {    System.out.println(i);    i++;}

C. do-while loop

int i = 1;
do
 {   
 System.out.println("Attempt: " + i);   
 i++;
}
 while (i <= 3);

Attempt: 1Attempt: 2Attempt: 3

D. break and continue

for (int i = 1; i <= 5; i++)
 {   
 if (i == 3) 
{     
   continue;  
  }    
if (i == 5)
 {        break;    }    
System.out.println(i);}

124

• continue skips the rest of the current iteration.
• break terminates the loop.

Automation testing example

String[] users = {    "user1", "user2", "user3", "user4", "user5"};
for (int i = 0; i < users.length; i++)
 {    
System.out.println("Testing login for " + users[i]);
}

8. Arrays and strings

A. Arrays

Example

public class ArrayExample 
{    
public static void main(String[] args)
 {       
 String[] browsers = {"Chrome", "Firefox", "Edge"};       
 System.out.println(browsers[0]);     
   System.out.println(browsers[1]);       
 System.out.println(browsers[2]);      
  System.out.println("Total browsers: " + browsers.length);   
 }
}

ChromeFirefoxEdgeTotal browsers: 3

• Array indexing starts from 0.
• browsers[0] is the first element.
• browsers.length gives the number of elements.
• Accessing an invalid index causes ArrayIndexOutOfBoundsException.

Loop through an array

String[] testCases = {"TC01", "TC02", "TC03"};
for (String testCase : testCases)
 {   
 System.out.println("Executing " + testCase);}

B. Strings

Common String methods

Example: Validate a message

String expected = "Login Successful";
String actual = "Login Successful";
if (actual.equals(expected)) 
{  
  System.out.println("Message validation passed");
}
else 
{    
System.out.println("Message validation failed");
}

Important difference: == and .equals()

String a = new String("Java");String b = new String("Java");System.out.println(a == b);      // falseSystem.out.println(a.equals(b)); // true

Automation testing example

9. Methods and parameters

What is a method?

Basic syntax

returnType methodName(parameters) {    // code}

Example 1: Method without parameters

public class MethodExample
 {    
static void greet() 
{        
System.out.println("Welcome to Java");   
 }  
  public static void main(String[] args) 
{       
 greet();       
 greet();  
  }
}

Welcome to JavaWelcome to Java

Example 2: Method with parameters

public class LoginExample {   
 static void login(String username, String password) 
{      
  System.out.println("Username: " + username);        
System.out.println("Password received");    
}   
 public static void main(String[] args)
 {       
 login("tester1", "demoPassword");    
}
}

• username and password are parameters.
• "tester1" and "demoPassword" are arguments passed to the method.

Example 3: Method with a return value

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

Automation testing example

void enterUsername(String username) 
{  
  // Locate the username field and enter the value
}
void clickLogin() 
{   
 // Locate and click the login button}

10. Classes and objects

What is a class?

What is an object?

Example

class Student
 {   
 String name;   
 int age;   
 void displayDetails() 
{       
 System.out.println("Name: " + name);      
  System.out.println("Age: " + age);    
}
}
public class Main 
{   
 public static void main(String[] args) 
{
        Student student1 = new Student();    
    student1.name = "Rahul";    
    student1.age = 25;      
  student1.displayDetails();   
 }
}

Name: RahulAge: 25

Understand this line

Student student1 = new Student();

• Student: The class type.
• student1: The variable that holds the object reference.
• new: Creates an object.
• Student(): Calls the constructor.

Automation testing example

class LoginPage 
{   
 void enterUsername() 
{       
 System.out.println("Entering username");    
}   
 void enterPassword()
 {       
 System.out.println("Entering password");  
  }   
 void clickLogin() 
{
        System.out.println("Clicking login");   
 }
}

11. Constructors

What is a constructor?

Constructor rules

• Its name must match the class name.
• It has no return type, not even void.
• It runs when an object is created using new.
• It can accept parameters.
• Constructors can be overloaded.

Example 1: No-argument constructor

class Employee 
{   
 String name;   
 Employee()
 {    
    name = "Unknown";   
 } 
   void display() 
{ 
       System.out.println(name); 
   }
}
public class Main
 {  
  public static void main(String[] args)
 {    
    Employee emp = new Employee(); 
       emp.display();    
}
}

Unknown

Example 2: Parameterized constructor

class Employee
 {    
String name;  
  int age;    
Employee(String employeeName, int employeeAge) 
{       
 name = employeeName;        
age = employeeAge;  
  }    
void display()
 {        
System.out.println(name + " - " + age);   
 }
}
public class Main {    public static void main(String[] args) 
{        
Employee emp1 = new Employee("Amit", 28);     
   Employee emp2 = new Employee("Priya", 25);       
 emp1.display();   
     emp2.display();   
 }
}

Amit - 28Priya - 25

Default constructor vs. no-argument constructor

Automation testing example

// Illustrative Selenium structureclass LoginPage 
{   
 // WebDriver driver;   
 // LoginPage(WebDriver driver)
 {   
 //     this.driver = driver;    // }}

12. Inheritance

What is inheritance?

• Parent class: The class whose members are inherited.
• Child class: The class that extends the parent.
• extends: Keyword used for class inheritance.

Example

class Animal

Animal is eating Dog is barking

Types of inheritance in Java

• Single: One child extends one parent.
• Multilevel: A class extends a class that itself extends another class.
• Hierarchical: Multiple child classes extend the same parent.
• Multiple inheritance of classes: Not supported directly in Java; similar behavior can be achieved through interfaces.

Automation testing example

class BaseTest

Opening applicationExecuting login test

class Animal
 {    
void eat()
 {       
 System.out.println("Animal is eating");   
 }
}
class Dog extends Animal
 {    
void bark() 
{        
System.out.println("Dog is barking"); 
   }
}
public class Main
 {   
 public static void main(String[] args)
 {       
 Dog dog = new Dog();       
 dog.eat();  // Inherited from Animal        dog.bark(); // Defined in Dog    }}

Animal is eatingDog is barking

class Animal
 {   
 void eat()
 {       
 System.out.println("Animal is eating");    
}
}
class Dog extends Animal 
{   
 void bark() 
{       
 System.out.println("Dog is barking");    
}
}
class Puppy extends Dog
 {   
 void play()
 {        
System.out.println("Puppy is playing");   
 }
}
public class Main 
{  
  public static void main(String[] args) 
{      
  Puppy puppy = new Puppy();       
 puppy.eat();  // From Animal       
 puppy.bark(); // From Dog      
  puppy.play(); // From Puppy    }}

Animal is eatingDog is barkingPuppy is playing

class Animal

Animal is eatingDog is barkingAnimal is eatingCat is meowingAnimal is eatingCow is mooing

class A {    void showA()
 {       
 System.out.println("A");    
}
}
class B
 {   
 void showB()
 {       
 System.out.println("B");   
 }
}
// Invalid Java:// class C extends A, B { }

interface Camera

Taking a photoPlaying music

class Calculator 
{    
int add(int a, int b)
 {   

30606.0

class Browser 
{ 
void open() 
{ 

Opening ChromeOpening Firefox

class BankAccount
 { 
  private double balance;   

1000.0

abstract class Payment {    abstract void pay(double amount);

Processing paymentCard payment: 500.0

interface Notification 
{   
 void sendMessage(String message);
}

Email: Test completedSMS: Test failed

abstract class BasePage
 {    
abstract void openPage();  

Page operation startedOpening home page

// Requires Selenium WebDriver dependency
WebDriver driver = new ChromeDriver();

public class ExceptionExample
 {   
 public static void main(String[] args) 
{   

Cannot divide by zeroProgram continues

try
 {   
 System.out.println("Executing test");
} 
catch (Exception e)

Executing testCleanup section

public class AgeCheck {  

Valid age

import java.io.IOException;class FileService {  

// Requires Selenium WebDriver dependencytry 
{    
driver.findElement(By.id("loginButton")).click();
} 
catch (NoSuchElementException e)
 {
    System.out.println("Login button was not found");
}

import java.util.ArrayList;import java.util.List;public class ListExample 

[Chrome, Firefox, Chrome]Firefox

import java.util.HashSet;import java.util.Set;public class SetExample 

import java.util.HashMap;import java.util.Map;public class MapExample

tester1Chrome

import java.util.ArrayList;public class ArrayListExample

Login Test[Login Test, Product Search Test]Size: 2

import java.util.HashMap;import java.util.Map;public class HashMapExample

tester1Browser: Chrome

Map<String, String> loginData = new HashMap<>();loginData.put("username", "testuser");

class Employee
 {    
static String company = "WebVittha";    String name;    Employee(String name) { this.name = name;

RahulPriyaWebVittha

class Calculator 
{   
 static int square(int number) 
{       
 return number * number;   

final int MAX_RETRIES = 3;// MAX_RETRIES = 5; // Compilation error

class Parent 
{
final void display() 
{
System.out.println("Parent method"); 

final class Utility {    void show() {        System.out.println("Utility class");   

class TestConfig {    static final int DEFAULT_TIMEOUT_SECONDS = 10;}

import java.io.IOException;import java.nio.file.Files;import java.nio.file.Path;public class WriteFileExample 
{    
public static void main(String[] args) throws IOException 
{        
Path path = Path.of("test-result.txt");       
 Files.writeString(path, "Login Test: PASS");        
System.out.println("File written successfully");    
}
}

File written successfully

Login Test: PASS

import java.io.IOException;import java.nio.file.Files;import java.nio.file.Path;public class ReadLinesExample 
{   
 public static void main(String[] args) throws IOException 
{
 Path path = Path.of("test-cases.txt");       
 for (String line : Files.readAllLines(path)) 
{ 
System.out.println(line); 
}    
}
}

username,passwordtester1,pass123tester2,pass456

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;
public class CSVExample 
{ 
   public static void main(String[] args) throws IOException 
{
        List<String> lines =                Files.readAllLines(Path.of("users.csv"));
        for (int i = 1; i < lines.size(); i++) 
{ 
           String[] values = lines.get(i).split(","); 
String username = values[0];  
 String password = values[1]; 
 System.out.println("Testing user: " + username);
}
 }
}

Testing user: tester1Testing user: tester2

1. Print a message

class User 
{
 String name;   
 User(String name) 
{
 this.name = name;  
}
}

Map<String, String> data = new HashMap<>();data.put("browser", "Chrome");
data.put("environment", "QA");
for (Map.Entry<String, String> entry : data.entrySet()) 
{
System.out.println(  entry.getKey() + " = " + entry.getValue()    );
}

String text = "Selenium";String reversed = new StringBuilder(text).reverse().toString();
System.out.println(reversed);

int number = 7;if (number % 2 == 0)
 {   
 System.out.println("Even");
} 
else
 {    
System.out.println("Odd");
}

import java.util.*;
List<Integer> numbers =        Arrays.asList(1, 2, 3, 2, 4, 1);
Set<Integer> seen = new HashSet<>();
for (int number : numbers)
 { 
   if (!seen.add(number)) 
{  
      System.out.println("Duplicate: " + number); 
}
}

Duplicate: 2Duplicate: 1

String expected = "PASS";String actual = "PASS";if (expected.equals(actual))
 {   
 System.out.println("Results match");} else 
{    
System.out.println("Results do not match");
}

// Requires Selenium WebDriver dependencyList<WebElement> links =       
driver.findElements(By.tagName("a"));
System.out.println("Total links: " + links.size());