Introduction: Why Java Is Needed for Automation Testing
Java is the most preferred programming language for automation testing in enterprise projects. Tools like Selenium WebDriver, TestNG, JUnit, Cucumber, Rest Assured, and CI/CD pipelines are heavily built around Java.
Why interviewers focus on Java for automation testing:
- Object-oriented language → perfect for framework design
- Platform independent (Windows, Linux, Mac)
- Huge ecosystem (Selenium, TestNG, Maven, Jenkins)
- Strong support for API + UI + DB automation
- Easy to maintain large test suites
That’s why java interview questions for automation testing are asked in almost every automation role—from 2 years to 10+ years experience.
Core Java Topics Required for Automation Testing
Before automation tools, interviewers check your Java fundamentals.
1. OOP Concepts (Very Important)
- Class & Object
- Inheritance
- Polymorphism
- Encapsulation
- Abstraction
2. Java Collections
- List → ArrayList, LinkedList
- Set → HashSet
- Map → HashMap, LinkedHashMap
3. Exception Handling
- try, catch, finally
- checked vs unchecked exceptions
- custom exceptions
4. Multithreading
- Thread class
- Runnable interface
- Synchronization
5. Java 8 Features
- Streams
- Lambda expressions
- forEach
Java Interview Questions for Automation Testing (Core Java)
1. Why Java is preferred for automation testing?
Java supports OOP, is platform-independent, and integrates easily with Selenium and TestNG.
2. What is JVM?
JVM executes Java bytecode and makes Java platform independent.
3. What is OOP?
Object Oriented Programming organizes code using objects for reusability and maintainability.
4. Explain inheritance with example.
class Browser {
void openBrowser() {
System.out.println(“Browser opened”);
}
}
class Chrome extends Browser {
void testApp() {
System.out.println(“Testing in Chrome”);
}
}
public class Test {
public static void main(String[] args) {
Chrome c = new Chrome();
c.openBrowser();
c.testApp();
}
}
Output:
Browser opened
Testing in Chrome
5. What is polymorphism?
Same method name with different behavior.
class Login {
void login() {
System.out.println(“Login with username”);
}
void login(String otp) {
System.out.println(“Login with OTP”);
}
}
6. What is encapsulation?
Wrapping data using private variables and public getters/setters.
7. Abstract class vs Interface?
| Abstract Class | Interface |
| Can have methods with body | Methods abstract by default |
| Supports constructor | No constructor |
| Partial abstraction | 100% abstraction (Java 7) |
8. What is ArrayList?
Dynamic array allowing duplicate values.
9. ArrayList vs LinkedList?
- ArrayList → Fast access
- LinkedList → Fast insertion/deletion
10. What is HashMap?
HashMap<String, String> map = new HashMap<>();
map.put(“browser”, “chrome”);
System.out.println(map.get(“browser”));
Output:
chrome
11. Checked vs Unchecked Exception?
- Checked → IOException
- Unchecked → NullPointerException
12. Exception handling example
try {
int a = 10 / 0;
} catch (ArithmeticException e) {
System.out.println(“Exception handled”);
}
Output:
Exception handled
13. What is multithreading?
Executing multiple threads simultaneously.
14. Thread vs Runnable?
Runnable is preferred as it supports multiple inheritance.
15. Java 8 Stream example
List<Integer> list = Arrays.asList(10,20,30);
list.stream().filter(x -> x > 15).forEach(System.out::println);
Output:
20
30
Selenium WebDriver Interview Questions (Java Based)
16. What is Selenium?
Selenium automates web applications for testing.
17. What is WebDriver?
WebDriver controls browser directly using browser drivers.
18. Selenium code to open browser
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
19. What are locators?
Locators identify web elements.
Types:
- id
- name
- className
- xpath
- cssSelector
20. XPath vs CSS Selector?
XPath supports backward traversal; CSS is faster.
21. Implicit vs Explicit Wait
driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.visibilityOf(element));
22. What is Page Object Model (POM)?
Each page has a separate class for locators and actions.
Java Selenium Coding Challenges (Interview Level)
23. Handle dropdown
Select select = new Select(driver.findElement(By.id(“country”)));
select.selectByVisibleText(“India”);
24. Handle alerts
Alert alert = driver.switchTo().alert();
alert.accept();
25. Take screenshot
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
26. Find broken links (basic)
List<WebElement> links = driver.findElements(By.tagName(“a”));
for(WebElement link : links) {
System.out.println(link.getAttribute(“href”));
}
Real-Time Automation Interview Scenarios
Scenario 1: Page Object Model Framework
- Base class → Driver setup
- Page classes → Locators
- Test classes → Test cases
- Utilities → Config, reports
Scenario 2: API + UI Validation
- Login using API
- Fetch token
- Validate dashboard UI data
Scenario 3: Database Validation
- Fetch data from DB
- Compare with UI values
JUnit Interview Questions
27. What is JUnit?
Unit testing framework for Java.
28. Common JUnit annotations?
- @Test
- @Before
- @After
TestNG Interview Questions
29. What is TestNG?
Testing framework inspired by JUnit and NUnit.
30. Important TestNG annotations?
- @Test
- @BeforeMethod
- @AfterMethod
- @BeforeSuite
31. What is DataProvider?
@DataProvider
public Object[][] loginData() {
return new Object[][] {{“user”,”pass”}};
}
32. TestNG priority example
@Test(priority = 1)
public void loginTest() {}
Selenium + Java + API Practical Example
Response response = RestAssured.get(“/users”);
System.out.println(response.getStatusCode());
Expected Output:
200
Framework Design Interview Questions
33. What is Hybrid Framework?
Combination of POM + Data-Driven + Keyword-Driven.
34. What is Cucumber?
BDD framework using Gherkin language.
35. CI/CD tools used in automation?
- Jenkins
- GitHub Actions
- Azure DevOps
Common Mistakes in Java Automation Interviews
- Weak OOP concepts
- No Selenium hands-on practice
- Not understanding framework flow
- Memorizing answers only
- Ignoring exception handling
1-Page Java Automation Revision Table
| Area | Key Focus |
| Core Java | OOP, Collections |
| Selenium | Locators, Waits |
| TestNG | Annotations, DataProvider |
| Framework | POM, Hybrid |
| API | Rest Assured |
| CI/CD | Jenkins |
FAQs – Java Interview Questions for Automation Testing
Q1. Is Java mandatory for Selenium automation?
Yes, Java is the most widely used language.
Q2. Is TestNG better than JUnit for automation?
Yes, TestNG supports parallel execution and reporting.
Q3. Are live coding questions asked?
Yes, basic Java + Selenium coding is common.
Q4. Is API testing required for automation roles?
Yes, modern automation roles expect API knowledge.