Introduction: Why Java Is Needed for Automation Testing
Java is one of the most widely used programming languages in software testing and automation. Almost every modern automation framework—Selenium, TestNG, JUnit, Cucumber, Rest Assured, and CI/CD pipelines—relies heavily on Java.
Why Java is essential for testers:
- Strong object-oriented programming (OOP) concepts for framework design
- Platform-independent (runs on Windows, Linux, Mac)
- Large ecosystem of testing libraries and tools
- Easy integration with UI, API, and database testing
- High demand in automation testing interviews
Because of this, java interview questions for testing are a core part of manual-to-automation and experienced automation interviews.
Core Java Topics Required for Testing
Before automation tools, interviewers evaluate your 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
- Thread class
- Runnable interface
- Synchronization
5. Java 8 Features
- Streams
- Lambda expressions
- forEach
Java Interview Questions for Testing – Core Java
1. Why Java is used in software testing?
Java supports automation frameworks, OOP concepts, and cross-platform execution.
2. What is JVM?
JVM executes Java bytecode and makes Java platform-independent.
3. What is OOP?
Object-Oriented Programming organizes code into reusable objects.
4. 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
5. What is polymorphism?
Same method name with different behavior.
class Login {
void login() {
System.out.println(“Login using password”);
}
void login(String otp) {
System.out.println(“Login using OTP”);
}
}
6. What is encapsulation?
Binding data and methods together using private variables and public methods.
7. Abstract class vs Interface?
| Abstract Class | Interface |
| Can have method body | Abstract methods (Java 7) |
| Supports constructor | No constructor |
| Partial abstraction | Full abstraction |
8. What is ArrayList?
Dynamic array that allows duplicate values.
9. ArrayList vs LinkedList?
- ArrayList → faster access
- LinkedList → faster 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 exceptions?
- 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 because Java does not support multiple inheritance.
15. Java Stream example
List<Integer> list = Arrays.asList(5, 15, 25);
list.stream().filter(x -> x > 10).forEach(System.out::println);
Output:
15
25
Selenium WebDriver Interview Questions (Java Based)
16. What is Selenium?
Selenium is an open-source tool for automating web applications.
17. What is WebDriver?
WebDriver directly interacts with browsers using browser drivers.
18. Code to open browser using Selenium
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
19. What are locators in Selenium?
Locators identify web elements.
Types:
- id
- name
- className
- xpath
- cssSelector
20. XPath vs CSS Selector?
XPath supports backward traversal; CSS is faster and simpler.
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 web page is represented as a separate Java class.
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 all links on a page
List<WebElement> links = driver.findElements(By.tagName(“a”));
System.out.println(links.size());
Real-Time Automation Interview Scenarios
Scenario 1: Page Object Model Framework Design
- Base class → driver setup
- Page classes → locators & actions
- Test classes → test execution
- Utilities → config, reports
Scenario 2: API + UI Validation
- Login via API
- Fetch token
- Validate UI dashboard data
Scenario 3: Database Validation
- Fetch values from DB
- Compare with UI displayed 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[][] {{“user1″,”pass1”}};
}
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, and keyword-driven frameworks.
34. What is Cucumber?
BDD framework using Gherkin syntax.
35. CI/CD tools used in testing?
- Jenkins
- GitHub Actions
- Azure DevOps
Common Mistakes in Java Testing Interviews
- Weak understanding of OOP concepts
- No hands-on Selenium coding
- Not knowing framework architecture
- Memorizing answers without practice
- Ignoring exception handling
1-Page Java Interview 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 Testing
Q1. Is Java mandatory for automation testing?
Yes, Java is the most commonly used language.
Q2. Is TestNG better than JUnit for automation?
Yes, TestNG supports parallel execution and reporting.
Q3. Are coding questions asked in testing interviews?
Yes, basic Java and Selenium coding is common.
Q4. Is API testing required for testers?
Yes, modern testing roles expect API knowledge.