Java Selenium Testing Interview Questions

Introduction: Why Java Is Needed for Automation Testing

Java is the backbone language for Selenium automation testing in most enterprise projects. When interviewers ask java selenium testing interview questions, they expect candidates to understand both:

• Core Java fundamentals
  
• How Java integrates with Selenium WebDriver
  
• Framework design and real-time automation challenges
  

Java is preferred in automation testing because it is:

• Object-oriented and reusable
  
• Platform independent
  
• Rich in libraries (Collections, Streams, Concurrency)
  
• Well supported by Selenium, TestNG, JUnit, Maven, Jenkins
  

Most automation interviews combine Java written + Selenium coding + scenario-based questions, making Java knowledge non-negotiable.

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Core Java Topics for Testing (Must-Know Areas)

1. Object-Oriented Programming (OOP)

• Encapsulation
  
• Inheritance
  
• Polymorphism
  
• Abstraction
  
• Interface vs Abstract class
  

2. Java Collections

• List, Set, Map
  
• ArrayList vs LinkedList
  
• HashMap vs Hashtable
  
• Iterator usage in automation
  

3. Exception Handling

• Checked vs Unchecked exceptions
  
• try-catch-finally
  
• throw vs throws
  
• Selenium exception handling
  

4. Multithreading

• Thread vs Runnable
  
• Synchronization
  
• Parallel execution in TestNG
  

5. Java Streams

• filter(), map(), reduce()
  
• Lambda expressions
  
• Data processing in automation
  

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Java Selenium Testing Interview Questions & Answers

Core Java – Fundamentals

1. What is Java?
Java is an object-oriented, platform-independent programming language used extensively in automation testing.

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2. Why Java is preferred for Selenium automation?

• Strong OOP support
  
• Large community
  
• Rich open-source ecosystem
  
• Easy integration with frameworks
  

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3. Difference between JDK, JRE, and JVM?

Component	Description
JVM	Executes bytecode
JRE	JVM + libraries
JDK	JRE + development tools

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OOP Interview Questions

4. What is encapsulation?
Binding data and methods together and restricting direct access.

class User {

    private String name;

    public void setName(String n) {

        name = n;

    }

    public String getName() {

        return name;

    }

}

Output:
No direct access to name

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5. Difference between abstraction and encapsulation?

Abstraction	Encapsulation
Hides implementation	Protects data
Uses interface/abstract	Uses private access

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6. Can we override static methods?
No, static methods belong to the class, not object.

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Collections Interview Questions

7. Difference between ArrayList and LinkedList?

ArrayList	LinkedList
Faster access	Faster insert/delete
Uses array	Uses doubly linked list

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8. Output-based question

Set<Integer> set = new HashSet<>();

set.add(10);

set.add(20);

set.add(10);

System.out.println(set.size());

Output:
2

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9. Why HashMap is used in frameworks?
To store test data as key-value pairs.

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Exception Handling

10. Checked vs Unchecked exceptions?

Checked	Unchecked
Compile-time	Runtime
IOException	NullPointerException

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11. Selenium exception example

try {

    driver.findElement(By.id(“btn”)).click();

} catch (NoSuchElementException e) {

    System.out.println(“Element not found”);

}

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Multithreading

12. How TestNG supports parallel execution?
Using parallel=”methods” in testng.xml.

<suite parallel=”methods” thread-count=”3″>

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13. Thread vs Runnable?

Thread	Runnable
Extends Thread	Implements Runnable
Limited inheritance	Flexible

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Java Streams

14. Stream example

List<String> names = Arrays.asList(“Ram”,”Sam”,”Raj”);

names.stream()

     .filter(n -> n.startsWith(“R”))

     .forEach(System.out::println);

Output:
Ram
Raj

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Java Selenium Coding Challenges

Locators

15. Types of Selenium locators

• ID
  
• Name
  
• ClassName
  
• XPath
  
• CSS Selector
  

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16. Dynamic XPath

//input[contains(@id,’email’)]

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Waits

17. Implicit vs Explicit Wait

Implicit	Explicit
Global	Element-specific
Less control	More control

WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));

wait.until(ExpectedConditions.visibilityOfElementLocated(By.id(“login”)));

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Browser Handling

18. Launch Chrome browser

WebDriver driver = new ChromeDriver();

driver.get(“https://example.com”);

System.out.println(driver.getTitle());

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Real-Time Automation Interview Scenarios

Scenario 1: Page Object Model (POM)

Question: Why POM is used?

Answer:

• Improves maintainability
  
• Reduces code duplication
  
• Enhances readability
  

public class LoginPage {

    WebDriver driver;

    By username = By.id(“user”);

    By password = By.id(“pass”);

    public LoginPage(WebDriver driver) {

        this.driver = driver;

    }

    public void login(String u, String p) {

        driver.findElement(username).sendKeys(u);

        driver.findElement(password).sendKeys(p);

    }

}

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Scenario 2: API + Database Validation

Problem:
Validate UI data with backend API and database.

Solution Approach:

1. Capture UI value using Selenium
   
2. Call API using RestAssured
   
3. Fetch DB data using JDBC
   
4. Compare values using assertions
   

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JUnit Interview Questions

19. What is JUnit?
JUnit is a unit testing framework for Java.

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20. Difference between @Before and @BeforeClass?

@Before	@BeforeClass
Runs before each test	Runs once

@Before

public void setup() {

    System.out.println(“Setup”);

}

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TestNG Interview Questions

21. Advantages of TestNG

• Parallel execution
  
• DataProvider
  
• Grouping
  
• Reports
  

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22. TestNG priority example

@Test(priority = 1)

public void loginTest() {}

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23. What is DataProvider?

@DataProvider

public Object[][] data() {

    return new Object[][] {{“user”,”pass”}};

}

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Selenium + Java + API Practical Example

Response response = RestAssured.get(“/users”);

Assert.assertEquals(response.getStatusCode(), 200);

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Framework Design Interview Questions

24. What is Hybrid Framework?
Combination of:

• Page Object Model
  
• Data-Driven
  
• Keyword-Driven
  

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25. Tools used in CI/CD

• Jenkins
  
• GitHub Actions
  
• Maven
  
• Git
  

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26. Cucumber usage?
Supports BDD using Gherkin language.

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Common Mistakes in Java Selenium Interviews

• Weak Java fundamentals
  
• Poor locator strategy
  
• Confusing waits
  
• No framework understanding
  
• Ignoring exception handling
  

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1-Page Revision Notes (Quick Table)

Topic	Key Points
Java	OOP, Collections
Selenium	Locators, waits
TestNG	Priority, DataProvider
Framework	POM, Hybrid
CI/CD	Jenkins, Git

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FAQs – Java Selenium Testing Interview Questions

Q1. Is Java mandatory for Selenium testing?
Yes, for most enterprise automation roles.

Q2. How many questions should I prepare?
At least 150+ java selenium testing interview questions.

Q3. Is framework knowledge compulsory?
Yes, especially POM and Hybrid frameworks.

Q4. Coding or theory – what matters more?
Both, but coding + scenarios carry more weight.