Introduction: Why Java Is Needed for Automation Testing
Java is one of the most important skills for software testers, especially those moving into automation testing roles. Most companies today expect testers to understand Java not just theoretically, but also practically, through coding, framework design, and real-time problem solving.
Java is widely used in testing because:
- Automation frameworks are built using Java + Selenium
- Strong OOP concepts help design maintainable frameworks
- Platform-independent (runs on Windows, Linux, macOS)
- Easy integration with UI, API, Database, and CI/CD
- Highly demanded in automation testing interviews
That’s why java questions for testing interview are asked in almost every QA, Automation Tester, and SDET interview.
Core Java Topics for Testing (Must-Know Areas)
Interviewers usually check these Core Java fundamentals before automation tools.
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 (Basic)
- Thread class
- Runnable interface
5. Java 8 Features
- Streams
- Lambda expressions
- forEach
Java Questions for Testing Interview – Core Java (With Answers)
Q1. Why is Java important for testing?
Java is used to write automation scripts, build frameworks, and integrate testing tools.
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 with different behavior (method overloading/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 it via getters/setters.
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?
Dynamic array that allows duplicate values.
Q9. ArrayList vs LinkedList?
- ArrayList → Faster access
- LinkedList → Faster insertion/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 exception?
- 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 at the same time.
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 Questions for Testing Interview
Q16. What is Selenium?
Selenium is an open-source tool used to automate 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?
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)
- Base class → Driver setup
- Page classes → Locators & methods
- Test classes → Validations
- Utilities → Config, reports
Scenario 2: Login Automation Test
Steps
- Launch browser
- Enter credentials
- 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 DB
- Compare with UI displayed values
JUnit Questions for Testing Interview
Q27. What is JUnit?
JUnit is a unit testing framework for Java.
Q28. Common JUnit annotations?
- @Test
- @Before
- @After
TestNG Questions for Testing Interview
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 (Frequently Asked)
Q33. What is Hybrid Framework?
Combination of POM, Data-Driven, and Keyword-Driven frameworks.
Q34. What is Cucumber?
BDD framework using Gherkin syntax (Given-When-Then).
Q35. CI/CD tools used in testing?
- Jenkins
- GitHub Actions
- Azure DevOps
Common Mistakes in Java Testing Interviews
- Weak OOP fundamentals
- Memorizing answers without coding practice
- Not understanding framework flow
- Missing waits and exception handling
- Hard-coding test data
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 – Java Questions for Testing Interview
Q1. Is Java mandatory for testing interviews?
Java is mandatory for automation testing roles.
Q2. Are Java coding questions asked in QA interviews?
Yes, especially for automation and SDET roles.
Q3. Is Selenium required with Java?
Yes, Selenium + Java is the most common automation stack.
Q4. Do testers need API testing knowledge?
Yes, modern testing roles expect API skills.