Introduction: Why Java Is Needed for Automation Testing
Java is one of the most widely used programming languages for test automation. Most enterprise automation frameworks are built using Java + Selenium, combined with TestNG or JUnit, and integrated with CI/CD tools.
Why interviewers prefer Java for automation testing:
- Platform-independent (Write once, run anywhere)
- Strong object-oriented programming (OOP) support
- Rich libraries and collections
- Excellent tool support (Selenium, TestNG, JUnit, Maven, Gradle)
- Easy integration with API, database, and CI/CD pipelines
Because of this, java automation testing interview questions are asked in almost every automation interview—from junior to senior levels.
Core Java Topics Required for Automation Testing
Before jumping into interview questions, you must clearly understand these core Java areas:
1. OOP Concepts (Very Important)
- Class & Object
- Inheritance
- Polymorphism
- Encapsulation
- Abstraction
2. Collections Framework
- List (ArrayList, LinkedList)
- Set (HashSet)
- Map (HashMap)
- Iterator vs ListIterator
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 Automation Testing Interview Questions and Answers (Core Java)
1. Why is Java used in automation testing?
Java is object-oriented, platform-independent, and well supported by automation tools like Selenium.
2. What is JVM?
JVM (Java Virtual Machine) runs Java bytecode on any operating system.
3. What is OOP?
OOP organizes code using objects to improve reusability and maintainability.
4. Explain inheritance with example.
Inheritance allows one class to acquire properties of another.
class Browser {
void open() {
System.out.println(“Browser opened”);
}
}
class Chrome extends Browser {
void test() {
System.out.println(“Testing in Chrome”);
}
}
Output:
Browser opened
Testing in Chrome
5. What is polymorphism?
Same method behaving differently.
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 and methods together using private variables and public methods.
7. Difference between abstract class and interface?
| Abstract Class | Interface |
| Can have methods with body | Only abstract methods (Java 7) |
| Supports constructor | No constructor |
8. What is ArrayList?
Resizable array used to store duplicate elements.
9. Difference between ArrayList and LinkedList?
- ArrayList: Fast retrieval
- LinkedList: Fast insertion/deletion
10. What is HashMap?
Stores key-value pairs without order.
HashMap<String, String> map = new HashMap<>();
map.put(“browser”, “chrome”);
System.out.println(map.get(“browser”));
Output:
chrome
11. Checked vs Unchecked Exception?
- Checked: Compile-time (IOException)
- Unchecked: Runtime (NullPointerException)
12. What is try-catch?
Handles runtime errors gracefully.
try {
int a = 10/0;
} catch (Exception e) {
System.out.println(“Error handled”);
}
13. What is multithreading?
Executing multiple threads simultaneously.
14. Thread vs Runnable?
Runnable is preferred as it supports multiple inheritance.
15. What is Java Stream?
Processes data collections efficiently.
list.stream().filter(x -> x > 10).forEach(System.out::println);
Selenium WebDriver Interview Questions (Java Based)
16. What is Selenium?
Selenium automates web applications for testing.
17. What is WebDriver?
WebDriver interacts directly with browsers.
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(10, TimeUnit.SECONDS);
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.visibilityOf(element));
22. What is Page Object Model (POM)?
Design pattern where each page has a separate class.
Java Selenium Coding Challenges (Interview Level)
23. Find broken links
List<WebElement> links = driver.findElements(By.tagName(“a”));
for(WebElement link : links) {
System.out.println(link.getAttribute(“href”));
}
24. Handle dropdown
Select s = new Select(driver.findElement(By.id(“country”)));
s.selectByVisibleText(“India”);
25. Handle alerts
Alert alert = driver.switchTo().alert();
alert.accept();
26. Take screenshot
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
TestNG Interview Questions
27. What is TestNG?
Testing framework inspired by JUnit and NUnit.
28. TestNG annotations?
- @Test
- @BeforeMethod
- @AfterMethod
- @BeforeSuite
29. Priority in TestNG
@Test(priority=1)
void loginTest() {}
30. What is DataProvider?
@DataProvider
public Object[][] data() {
return new Object[][] {{“user1″,”pass1”}};
}
JUnit Interview Questions
31. What is JUnit?
Unit testing framework for Java.
32. JUnit annotations?
- @Test
- @Before
- @After
Real-Time Automation Interview Scenarios
Scenario 1: POM Framework Design
- Base class (driver setup)
- Page classes (locators)
- Test classes (test cases)
- Utilities (config, screenshots)
Scenario 2: API + UI Validation
- Login via API
- Validate dashboard UI
- Compare API response with UI data
Scenario 3: Database Validation
- Fetch data from DB
- Compare with UI displayed values
Selenium + Java + API Practical Example
Response res = RestAssured.get(“/users”);
System.out.println(res.getStatusCode());
Common Mistakes in Java Automation Interviews
- Weak OOP concepts
- Not understanding framework flow
- No hands-on Selenium coding
- Memorizing answers without practice
- Ignoring exception handling
1-Page Java Automation Revision Sheet
| Topic | Key Points |
| OOP | Inheritance, Polymorphism |
| Collections | List, Set, Map |
| Selenium | Locators, Waits |
| TestNG | Annotations, DataProvider |
| Framework | POM, Hybrid |
| CI/CD | Jenkins integration |
FAQs – Java Automation Testing Interview Questions
Q1. Is Java mandatory for Selenium automation?
Yes, Java is the most commonly used language.
Q2. Is TestNG better than JUnit?
Yes, for automation frameworks.
Q3. Do interviews include live coding?
Yes, basic Selenium + Java coding is common.
Q4. Is API testing required for automation roles?
Yes, modern roles expect API knowledge.