Introduction: Why Java Is Needed for Automation Testing
In most companies, Java machine tests are used to evaluate how well a candidate can write code, solve problems, and build automation logic in real time. Unlike theoretical interviews, a machine test checks your hands-on skills.
Java is the most preferred language for automation testing machine rounds because:
- Most automation frameworks are built using Java
- Java supports OOP concepts, essential for framework design
- Strong integration with Selenium, TestNG, JUnit, Rest Assured
- Easy CI/CD execution using Jenkins or GitHub Actions
- Widely accepted in service-based and product companies
That’s why java machine test interview questions usually combine:
- Core Java coding
- Selenium automation tasks
- Framework design logic
- API + database validation scenarios
Core Java Topics for Testing (Must for Machine Test)
Before automation, interviewers test Java fundamentals.
1. OOP Concepts
- Class & Object
- Inheritance
- Polymorphism
- Encapsulation
- Abstraction
2. Collections Framework
- 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
Java Machine Test Interview Questions with Answers (Core Java)
Q1. Why is Java preferred in machine tests?
Java allows interviewers to test OOP concepts, collections, exception handling, and automation logic in one language.
Q2. What is JVM?
JVM executes Java bytecode and makes Java platform-independent.
Q3. Explain OOP in simple terms.
OOP organizes code into objects to improve reuse and maintainability.
Q4. Write a Java program to demonstrate inheritance.
class Browser {
void open() {
System.out.println(“Browser opened”);
}
}
class Chrome extends Browser {
void test() {
System.out.println(“Testing in Chrome”);
}
}
public class Test {
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.
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 via getters/setters.
Q7. Difference between abstract class and interface?
| Abstract Class | Interface |
| Can have method body | Methods abstract (Java 7) |
| Supports constructor | No constructor |
| Partial abstraction | Full abstraction |
Q8. What is ArrayList?
A dynamic array that allows duplicate elements.
Q9. ArrayList vs LinkedList?
- ArrayList → Fast access
- LinkedList → Fast insertion/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. Checked vs Unchecked exception?
- Checked → IOException
- Unchecked → NullPointerException
Q12. Write exception handling code.
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 as Java does not support multiple inheritance.
Q15. Java 8 stream example.
List<Integer> nums = Arrays.asList(5,15,25);
nums.stream().filter(x -> x > 10).forEach(System.out::println);
Output
15
25
Java Selenium Machine Test Coding Challenges
Q16. Open a browser using Selenium.
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
Q17. Locate an element using XPath.
driver.findElement(By.xpath(“//input[@id=’username’]”)).sendKeys(“admin”);
Q18. Handle dropdown.
Select s = new Select(driver.findElement(By.id(“country”)));
s.selectByVisibleText(“India”);
Q19. Handle alert.
Alert alert = driver.switchTo().alert();
alert.accept();
Q20. Apply implicit and explicit waits.
driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.visibilityOf(element));
Q21. Take screenshot.
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
Q22. Find all links on a page.
List<WebElement> links = driver.findElements(By.tagName(“a”));
System.out.println(links.size());
Real-Time Java Machine Test Scenarios
Scenario 1: Page Object Model (POM) Implementation
Expected approach
- Base class → WebDriver setup
- Page class → locators + methods
- Test class → assertions
Interview focus
- Code structure
- Reusability
- Clean design
Scenario 2: Login Automation Test
Steps
- Launch browser
- Enter credentials
- Click login
- Validate dashboard
Scenario 3: API + UI Validation
Steps
- Call login API
- Capture token
- Validate UI dashboard data
Scenario 4: Database Validation
Steps
- Fetch DB records
- Compare with UI values
JUnit Machine Test Interview Questions
Q23. What is JUnit?
JUnit is a unit testing framework for Java.
Q24. Common JUnit annotations?
- @Test
- @Before
- @After
TestNG Machine Test Interview Questions
Q25. What is TestNG?
TestNG is an advanced testing framework inspired by JUnit.
Q26. Important TestNG annotations?
- @Test
- @BeforeMethod
- @AfterMethod
- @BeforeSuite
Q27. DataProvider example.
@DataProvider
public Object[][] data(){
return new Object[][] {{“user”,”pass”}};
}
Q28. 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 in Java Machine Tests
Q29. What is Hybrid Framework?
Combination of POM + Data-Driven + Keyword-Driven frameworks.
Q30. What is Cucumber?
BDD framework using Gherkin syntax (Given-When-Then).
Q31. CI/CD tools used in automation?
- Jenkins
- GitHub Actions
- Azure DevOps
Common Mistakes in Java Machine Test Interviews
- Writing unstructured code
- Weak OOP concepts
- No proper waits in Selenium
- Hard-coding test data
- Poor exception handling
- Ignoring framework design
1-Page Revision Table / Notes
| Area | Key Focus |
| Core Java | OOP, Collections |
| Selenium | Locators, Waits |
| TestNG/JUnit | Annotations |
| Framework | POM, Hybrid |
| API | Rest Assured |
| CI/CD | Jenkins |
FAQs – Java Machine Test Interview Questions
Q1. What is tested in a Java machine round?
Core Java coding, Selenium automation, framework logic, and problem solving.
Q2. Is Selenium mandatory for Java machine tests?
Yes, most automation machine tests include Selenium tasks.
Q3. Are API questions asked in machine tests?
Yes, especially for experienced automation roles.
Q4. How long is a Java machine test?
Typically 60–120 minutes.