Introduction: Why Java Is Needed for Automation Testing
Java is the most widely used programming language in automation testing. Most enterprise automation frameworks are built using Java + Selenium, supported by tools such as TestNG, JUnit, Cucumber, Rest Assured, Maven, and Jenkins.
Interviewers prefer Java for automation testing because:
- Java has strong Object-Oriented Programming (OOP) concepts
- It is platform-independent (Windows, Linux, macOS)
- Easy to design scalable and maintainable automation frameworks
- Seamless integration with UI, API, database, and CI/CD pipelines
- High demand for Java-based Automation Testers and SDETs
That’s why automation testing interview questions on Java are a mandatory part of QA and automation interviews.
Core Java Topics for Automation Testing
Before moving to Selenium or frameworks, interviewers first test Core Java fundamentals.
1. OOP Concepts
- Class and 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
4. Multithreading (Basics)
- Thread class
- Runnable interface
5. Java 8 Features
- Streams
- Lambda expressions
- forEach()
Automation Testing Interview Questions on Java – Core Java (With Answers)
Q1. Why is Java used in automation testing?
Java supports automation frameworks, OOP design, and cross-platform execution.
Q2. What is JVM?
JVM (Java Virtual Machine) executes Java bytecode and makes Java platform-independent.
Q3. What is OOP?
Object-Oriented Programming organizes code into reusable objects.
Q4. Explain inheritance with example.
class Browser {
void open() {
System.out.println(“Browser opened”);
}
}
class Chrome extends Browser {
void test() {
System.out.println(“Testing in Chrome”);
}
}
public class Demo {
public static void main(String[] args) {
Chrome c = new Chrome();
c.open();
c.test();
}
}
Output
Browser opened
Testing in Chrome
Q5. What is polymorphism?
Same method name behaving differently (method overloading or overriding).
class Login {
void login() {
System.out.println(“Login with password”);
}
void login(String otp) {
System.out.println(“Login with OTP”);
}
}
Q6. What is encapsulation?
Wrapping data using private variables and accessing them using public methods.
Q7. Abstract class vs Interface?
| Abstract Class | Interface |
| Can have method body | Methods abstract by default (Java 7) |
| Constructor allowed | No constructor |
| Partial abstraction | Full abstraction |
Q8. What is ArrayList?
A dynamic array that allows duplicate values.
Q9. ArrayList vs LinkedList?
- ArrayList → Faster access
- LinkedList → Faster insertion and deletion
Q10. What is HashMap?
HashMap<String,String> map = new HashMap<>();
map.put(“env”,”QA”);
System.out.println(map.get(“env”));
Output
QA
Q11. Checked vs Unchecked exceptions?
- Checked → IOException
- Unchecked → NullPointerException
Q12. Exception handling example.
try {
int a = 10 / 0;
} catch (ArithmeticException e) {
System.out.println(“Exception handled”);
}
Output
Exception handled
Q13. What is multithreading?
Executing multiple threads simultaneously.
Q14. Thread vs Runnable?
Runnable is preferred because Java does not support multiple inheritance.
Q15. 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 + Java Automation Interview Questions
Q16. What is Selenium?
Selenium is an open-source tool for automating web applications.
Q17. What is WebDriver?
WebDriver controls browsers directly using browser drivers.
Q18. Selenium code to open browser.
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
Q19. What are locators in Selenium?
Locators identify web elements.
Types:
- id
- name
- className
- xpath
- cssSelector
Q20. XPath vs CSS Selector?
XPath supports backward traversal; CSS is faster and simpler.
Q21. Implicit vs Explicit wait.
driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.visibilityOf(element));
Java Selenium Coding Challenges (Interview Level)
Q22. Handle dropdown.
Select select = new Select(driver.findElement(By.id(“country”)));
select.selectByVisibleText(“India”);
Q23. Handle alert.
Alert alert = driver.switchTo().alert();
alert.accept();
Q24. Take screenshot.
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
Q25. Find all links on a page.
List<WebElement> links = driver.findElements(By.tagName(“a”));
System.out.println(links.size());
Q26. File handling example.
BufferedReader br = new BufferedReader(new FileReader(“data.txt”));
System.out.println(br.readLine());
Real-Time Interview Scenarios (Automation Problem Solving)
Scenario 1: Page Object Model (POM)
Design
- Base class → WebDriver setup
- Page classes → Locators & actions
- Test classes → Assertions
- Utilities → Config, reports
Scenario 2: Login Automation Test
Steps
- Launch browser
- Enter username and password
- Click Login
- Validate dashboard page
Scenario 3: API + UI Validation
- Call login API
- Capture token
- Validate UI data with API response
Scenario 4: Database Validation
- Fetch data from database
- Compare with UI displayed values
JUnit Interview Questions
Q27. What is JUnit?
JUnit is a unit testing framework for Java.
Q28. Common JUnit annotations?
- @Test
- @Before
- @After
TestNG Interview Questions
Q29. What is TestNG?
TestNG is an advanced testing framework inspired by JUnit and NUnit.
Q30. Important TestNG annotations?
- @Test
- @BeforeMethod
- @AfterMethod
- @BeforeSuite
Q31. DataProvider example.
@DataProvider
public Object[][] loginData() {
return new Object[][] {{“user”,”pass”}};
}
Q32. TestNG priority example.
@Test(priority = 1)
public void loginTest() {}
Selenium + Java + API Practical Example
Response response = RestAssured.get(“/users”);
System.out.println(response.getStatusCode());
Output
200
Framework Design Questions (Very Important)
Q33. What is Hybrid Framework?
Combination of POM + Data-Driven + Keyword-Driven frameworks.
Q34. What is Cucumber?
BDD framework using Gherkin syntax (Given-When-Then).
Q35. CI/CD tools used in automation testing?
- Jenkins
- GitHub Actions
- Azure DevOps
Common Mistakes in Java Automation Interviews
- Weak Core Java fundamentals
- No hands-on Selenium coding
- Hard-coded test data
- Missing waits and exception handling
- Poor framework understanding
1-Page Revision Table / Notes
| Area | Key Focus |
| Core Java | OOP, Collections, Streams |
| Selenium | Locators, Waits |
| TestNG/JUnit | Annotations, DataProvider |
| Framework | POM, Hybrid, Cucumber |
| API | Rest Assured |
| CI/CD | Jenkins |
FAQs – Automation Testing Interview Questions on Java
Q1. Is Java mandatory for automation testing interviews?
Yes, Java is the most commonly expected language.
Q2. Are Java coding questions asked in interviews?
Yes, Core Java and Selenium coding are very common.
Q3. Is TestNG better than JUnit for automation?
Yes, TestNG supports parallel execution and advanced reporting.
Q4. Do automation testers need API testing knowledge?
Yes, modern automation roles require API skills.