Introduction: Why Java Is Needed for Automation Testing
In modern QA and SDET interviews, Core Java is not optional—it is a foundational skill. Even if the role is titled Automation Tester or QA Engineer, interviewers expect strong knowledge of Core Java concepts before moving to Selenium, TestNG, or frameworks.
Java is essential for automation testing because:
- Automation scripts and frameworks are written using Core Java
- Java’s OOP principles help design reusable and scalable frameworks
- It integrates smoothly with Selenium WebDriver, TestNG, JUnit, Cucumber
- Supports UI, API, database, and CI/CD automation
- Widely used in enterprise-level automation projects
That’s why interview questions on core java for automation testing are asked in almost every automation interview, from fresher to experienced level.
Core Java Topics for Automation Testing (Interview Focus Areas)
Interviewers usually evaluate testers on these Core Java building blocks.
1. Object-Oriented Programming (OOP)
- Class and Object
- Inheritance
- Polymorphism
- Encapsulation
- Abstraction
2. Java Collections Framework
- List → ArrayList, LinkedList
- Set → HashSet
- Map → HashMap, LinkedHashMap
3. Exception Handling
- try, catch, finally
- Checked vs Unchecked exceptions
4. Multithreading (Basic Level)
- Thread class
- Runnable interface
5. Java 8 Features
- Streams
- Lambda expressions
- forEach()
Interview Questions on Core Java for Automation Testing (With Answers & Code)
Q1. Why is Core Java important for automation testing?
Core Java is used to write automation scripts, handle test data, implement logic, and design automation frameworks.
Q2. What is JVM?
JVM (Java Virtual Machine) executes Java bytecode and makes Java platform-independent.
Q3. What is Object-Oriented Programming (OOP)?
OOP organizes code into objects to improve reusability, maintainability, and scalability.
Q4. Explain inheritance with a Java example.
class Browser {
void open() {
System.out.println(“Browser opened”);
}
}
class Chrome extends Browser {
void test() {
System.out.println(“Testing application in Chrome”);
}
}
public class Test {
public static void main(String[] args) {
Chrome c = new Chrome();
c.open();
c.test();
}
}
Output
Browser opened
Testing application in Chrome
Q5. What is polymorphism?
Polymorphism allows the same method name to perform different actions.
class Login {
void login() {
System.out.println(“Login using password”);
}
void login(String otp) {
System.out.println(“Login using OTP”);
}
}
Q6. What is encapsulation?
Encapsulation hides data using private variables and exposes it through public methods.
Q7. Difference between abstract class and interface?
| Abstract Class | Interface |
| Can have method body | Methods abstract by default |
| Constructor allowed | No constructor |
| Partial abstraction | Full abstraction |
Q8. What is an ArrayList?
ArrayList is a dynamic array that allows duplicate values.
Q9. ArrayList vs LinkedList?
- ArrayList → Faster access
- LinkedList → Faster insertion and deletion
Q10. Write a HashMap example.
HashMap<String,String> map = new HashMap<>();
map.put(“browser”,”chrome”);
System.out.println(map.get(“browser”));
Output
chrome
Q11. What are checked and 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?
Multithreading allows multiple threads to run concurrently.
Q14. Thread vs Runnable?
Runnable is preferred because Java does not support multiple inheritance.
Q15. Java 8 Stream example.
List<Integer> nums = Arrays.asList(10,20,30);
nums.stream().filter(n -> n > 15).forEach(System.out::println);
Output
20
30
Selenium + Core Java 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 Java code to open a browser.
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
Q19. What are locators in Selenium?
Locators identify web elements such as:
- id
- name
- className
- xpath
- cssSelector
Q20. XPath vs CSS Selector?
XPath supports backward traversal; CSS selectors are 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 in Selenium.
Select select = new Select(driver.findElement(By.id(“country”)));
select.selectByVisibleText(“India”);
Q23. Handle alert popup.
Alert alert = driver.switchTo().alert();
alert.accept();
Q24. Take screenshot using Selenium.
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
Q25. Find all links on a web page.
List<WebElement> links = driver.findElements(By.tagName(“a”));
System.out.println(links.size());
Q26. Java file handling example.
BufferedReader br = new BufferedReader(new FileReader(“data.txt”));
System.out.println(br.readLine());
Real-Time Interview Scenarios (Automation Testing)
Scenario 1: Page Object Model (POM)
- Base class → WebDriver setup
- Page classes → Locators and actions
- Test classes → Assertions
- Utilities → Config, reports
Scenario 2: Login Automation Flow
- Launch browser
- Enter username and password
- Click Login
- Validate dashboard page
Scenario 3: API + UI Validation
- Call API
- Capture response
- Validate UI data with API response
Scenario 4: Database Validation
- Fetch database values
- Compare with UI displayed data
JUnit Interview Questions for Automation Testing
Q27. What is JUnit?
JUnit is a unit testing framework for Java.
Q28. Common JUnit annotations?
- @Test
- @Before
- @After
TestNG Interview Questions for Automation Testing
Q29. What is TestNG?
TestNG is an advanced testing framework inspired by JUnit.
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?
Hybrid framework is a combination of POM + Data-Driven + Keyword-Driven frameworks.
Q34. What is Cucumber?
Cucumber is a BDD framework using Gherkin syntax (Given–When–Then).
Q35. CI/CD tools used in automation testing?
- Jenkins
- GitHub Actions
- Azure DevOps
Common Mistakes in Core Java Automation Interviews
- Weak understanding of OOP concepts
- Memorizing answers without coding practice
- Poor Selenium synchronization
- Hard-coded test data
- Lack of framework knowledge
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 – Interview Questions on Core Java for Automation Testing
Q1. Is Core Java mandatory for automation testing interviews?
Yes, Core Java is the backbone of automation frameworks.
Q2. Are Java coding questions asked in automation interviews?
Yes, both Core Java and Selenium coding questions are common.
Q3. Is TestNG better than JUnit for automation testing?
Yes, TestNG supports parallel execution and advanced reporting.
Q4. Do automation testers need API testing knowledge?
Yes, modern automation roles expect API testing skills.