Introduction: Why Java Is Needed for Automation Testing
In modern software testing, manual testing alone is not enough. Most companies expect testers to understand automation testing, and Java is the most commonly used programming language for this purpose.
Java is important for software testers because:
- Selenium automation frameworks are primarily built using Java
- Java helps testers write logic-based test scripts
- Core Java concepts are heavily tested in interviews
- Java integrates easily with Selenium, TestNG, JUnit, Maven, Jenkins
That’s why basic Java questions for software testing interview are asked even for freshers and manual testers transitioning to automation.
Core Java Topics for Testing
Before jumping into interview questions, let’s understand what interviewers expect from testers in Java.
1. Object-Oriented Programming (OOP)
Used for:
- Automation framework design
- Reusability of test scripts
- Maintainable code
Concepts:
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
2. Collections Framework
Used to store:
- Test data
- WebElements
- API responses
- Database values
Commonly used:
- List
- Set
- Map
3. Multithreading
Used for:
- Parallel execution of test cases
- Faster regression testing
4. Exception Handling
Used to:
- Handle automation failures
- Prevent test crashes
- Debug issues easily
5. Java 8 Streams
Used for:
- Filtering data
- Cleaner test logic
- Validating API and DB results
Basic Java Questions for Software Testing Interview (With Answers)
Core Java Interview Questions (1–30)
1. What is Java?
Java is a platform-independent, object-oriented programming language used widely in automation testing.
2. Why should a software tester learn Java?
Java helps testers:
- Write automation scripts
- Understand Selenium frameworks
- Crack automation interviews
3. What is JVM?
JVM (Java Virtual Machine) executes Java bytecode and makes Java platform independent.
4. Difference between JDK, JRE, and JVM?
| Component | Purpose |
| JVM | Executes bytecode |
| JRE | JVM + libraries |
| JDK | JRE + compiler |
5. What are OOP concepts?
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
6. What is encapsulation?
Wrapping data and methods into a single unit.
class User {
private String name;
public String getName() {
return name;
}
}
Expected Output:
Data is accessed securely using a getter.
7. What is inheritance?
One class acquiring properties of another class.
class BaseTest {
void setup() {
System.out.println(“Setup done”);
}
}
class LoginTest extends BaseTest {
void execute() {
setup();
System.out.println(“Login test executed”);
}
}
Output:
Setup done
Login test executed
8. What is polymorphism?
Same method name, different behavior.
9. What is abstraction?
Hiding implementation details and showing only functionality.
10. Abstract class vs interface?
| Abstract Class | Interface |
| Partial abstraction | Full abstraction |
| Can have methods | Defines contract |
11. What is a constructor?
A block that initializes an object.
12. What is static keyword?
Belongs to class, not object.
13. What is final keyword?
Used to restrict modification.
14. Why is String immutable?
For security and performance.
15. String vs StringBuilder?
| String | StringBuilder |
| Immutable | Mutable |
| Slower | Faster |
16. What is exception?
An unwanted event that interrupts program flow.
17. Checked vs unchecked exception?
| Checked | Unchecked |
| Compile time | Runtime |
| IOException | NullPointerException |
18. What is try-catch?
Used to handle exceptions.
19. What is collection framework?
Used to store and manipulate objects dynamically.
20. List vs Set?
| List | Set |
| Allows duplicates | No duplicates |
| Ordered | Unordered |
21. ArrayList vs LinkedList?
| ArrayList | LinkedList |
| Faster access | Faster insertion |
22. What is HashMap?
Stores data in key-value format.
23. HashMap example:
Map<String,String> data = new HashMap<>();
data.put(“username”,”admin”);
System.out.println(data.get(“username”));
Output:
admin
24. What is multithreading?
Running multiple threads simultaneously.
25. Why multithreading in automation?
To run test cases in parallel.
26. Thread vs Runnable?
Runnable is preferred.
27. What is synchronization?
Controls thread access to shared resources.
28. What is Java 8 stream?
List<Integer> nums = Arrays.asList(1,2,3,4);
nums.stream().filter(n -> n%2==0).forEach(System.out::println);
Output:
2
4
29. What is file handling?
Reading and writing files in Java.
30. File reading example:
BufferedReader br = new BufferedReader(new FileReader(“data.txt”));
System.out.println(br.readLine());
Java Selenium Coding Questions (31–55)
31. What is Selenium?
Selenium is an automation tool for web applications.
32. Why Selenium with Java?
Java provides stability and strong framework support.
33. Launch browser in Selenium:
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
34. What are Selenium locators?
id, name, className, xpath, cssSelector
35. XPath example:
//input[@id=’email’]
36. What are waits in Selenium?
Implicit, Explicit, Fluent
37. Explicit wait example:
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.visibilityOfElementLocated(By.id(“login”)));
38. Thread.sleep vs wait?
| Thread.sleep | Wait |
| Static | Dynamic |
39. Handle dropdown:
Select s = new Select(element);
s.selectByVisibleText(“India”);
40. Handle alert:
driver.switchTo().alert().accept();
41. Handle frames?
driver.switchTo().frame(0);
42. Take screenshot:
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
43. What is POM?
Page Object Model separates UI and test logic.
44. POM example:
@FindBy(id=”username”)
WebElement username;
45. What is Hybrid framework?
Combination of POM + Data-driven + Keyword-driven.
46. Maven usage?
Dependency management.
47. Maven lifecycle?
clean → test → install
48. Jenkins role?
CI/CD automation.
49. Git usage?
Version control.
50. Logging tool?
Log4j.
51. Reporting tool?
Extent Reports.
52. Headless browser?
Runs without UI.
53. Selenium limitation?
Cannot automate CAPTCHA.
54. Selenium Grid?
Parallel execution.
55. Test data sources?
Excel, JSON, Database.
JUnit & TestNG Interview Questions (56–70)
56. What is TestNG?
Testing framework inspired by JUnit.
57. Advantages of TestNG?
Parallel execution, annotations, reports.
58. Common TestNG annotations?
| Annotation | Purpose |
| @Test | Test case |
| @BeforeMethod | Setup |
| @AfterMethod | Teardown |
59. DataProvider example:
@DataProvider
public Object[][] data() {
return new Object[][]{{“admin”,”123″}};
}
60. Hard vs Soft assertion?
| Hard | Soft |
| Stops execution | Continues |
61. TestNG XML?
Controls execution.
62. What is JUnit?
Unit testing framework.
63. JUnit annotations?
@Test, @Before, @After
64. JUnit vs TestNG?
| JUnit | TestNG |
| Simple | Advanced |
65. Grouping tests?
Execute by category.
66. Retry Analyzer?
Re-runs failed tests.
67. Listener?
Captures test execution events.
68. BDD framework?
Cucumber.
69. Feature file?
Written in Gherkin.
70. Step definition?
Maps steps to code.
Real-Time Interview Scenarios (71–85)
71. Login automation scenario
- Read data from Excel
- Login
- Validate dashboard
72. UI + DB validation
Compare UI value with database value.
73. API + UI validation
Create data via API, verify in UI.
74. Parallel execution scenario
Using TestNG XML.
75. CI/CD scenario
Trigger automation from Jenkins.
76. Handling flaky tests
Explicit waits + retries.
77. Environment handling
Using config files.
78. Screenshot on failure
Used in reporting.
79. Logging importance
Debugging failures.
80. Framework maintenance
Reusable utilities.
81. Dynamic elements
Handled using waits.
82. Pop-up handling
Alert or window handling.
83. File upload
sendKeys(filePath)
84. Cross-browser testing
Chrome, Firefox, Edge.
85. Regression execution
Automated via CI/CD.
Common Mistakes in Java Interviews
- Weak OOP understanding
- Memorizing answers
- No coding practice
- Ignoring Selenium basics
- No real-time explanation
1-Page Revision Table / Notes
| Area | Focus |
| Core Java | OOP, Collections |
| Selenium | Locators, Waits |
| TestNG | Annotations |
| Framework | POM, Hybrid |
| CI/CD | Jenkins |
FAQs (For Google Ranking)
Is Java mandatory for software testing interviews?
Yes, especially for automation roles.
Are basic Java questions enough for freshers?
Yes, with Selenium basics.
Is coding required?
Basic Java coding is expected.
Is TestNG compulsory?
Yes, most automation frameworks use it.