Q11: How to Merge Two Sorted Arrays in Java?
Answer:
Merging two sorted arrays into a single sorted array is a common coding interview question. This is similar to the merge step of merge sort.
Java Code:
java
public class MergeSortedArrays {
public static int[] merge(int[] arr1, int[] arr2) {
int n1 = arr1.length, n2 = arr2.length;
int[] result = new int[n1 + n2];
int i = 0, j = 0, k = 0;
while (i < n1 && j < n2) {
result[k++] = (arr1[i] <= arr2[j]) ? arr1[i++] : arr2[j++];
}
while (i < n1) result[k++] = arr1[i++];
while (j < n2) result[k++] = arr2[j++];
return result;
}
public static void main(String[] args) {
int[] merged = merge(new int[]{1, 3, 5}, new int[]{2, 4, 6});
System.out.println(“Merged Array: ” + java.util.Arrays.toString(merged));
}
}
Output:
Merged Array: [1, 2, 3, 4, 5, 6]
🔹 Q12: How to Convert List to Set and Vice Versa in Java?
Answer:
- List to Set: Removes duplicates.
- Set to List: Allows indexing and preserves elements.
Java Code:
java
import java.util.*;
public class CollectionConverter {
public static void main(String[] args) {
List<String> names = Arrays.asList(“Alice”, “Bob”, “Alice”);
Set<String> uniqueNames = new HashSet<>(names);
List<String> finalList = new ArrayList<>(uniqueNames);
System.out.println(“List to Set: ” + uniqueNames);
System.out.println(“Set to List: ” + finalList);
}
}
Output:
List to Set: [Alice, Bob]
Set to List: [Alice, Bob]
🔹 Q13: What is the Difference Between ArrayList, HashSet, and HashMap?
Answer:
- ArrayList: Maintains insertion order, allows duplicates.
- HashSet: No duplicates, unordered.
- HashMap: Key-value pairs, keys are unique.
Example Code:
java
ArrayList<String> list = new ArrayList<>(List.of(“A”, “B”, “A”));
HashSet<String> set = new HashSet<>(list);
HashMap<String, Integer> map = new HashMap<>();
map.put(“Apple”, 1);
map.put(“Banana”, 2);
🔹 Q14: How to Remove All Whitespaces from a String in Java?
Answer:
Use replaceAll() or StringBuilder with Character.isWhitespace().
Code (Regex):
java
String input = ” Java Code “;
String cleaned = input.replaceAll(“\\s+”, “”);
System.out.println(cleaned); // JavaCode
🔹 Q15: How to Extract Only Digits from an Alphanumeric String in Java?
Answer:
Use either regex or manual iteration using Character.isDigit().
Java Code:
java
String mixed = “abc123def456”;
String digits = mixed.replaceAll(“[^0-9]”, “”);
System.out.println(digits); // 123456
🔹 Q16: How to Read Excel Data in Java using Apache POI?
Answer:
Apache POI allows reading .xlsx files using XSSFWorkbook.
Dependencies:
- poi-5.2.3.jar
- poi-ooxml-5.2.3.jar
Sample Code:
java
FileInputStream fis = new FileInputStream(“data.xlsx”);
Workbook wb = new XSSFWorkbook(fis);
Sheet sheet = wb.getSheetAt(0);
for (Row row : sheet) {
for (Cell cell : row) {
System.out.print(cell.toString() + “\t”);
}
System.out.println();
}
🔹 Q17: How to Capture Screenshot in Selenium using Java?
Answer:
Use TakesScreenshot interface to capture webpage screenshot.
Java Code:
java
WebDriver driver = new ChromeDriver();
driver.get(“https://example.com”);
File src = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
FileUtils.copyFile(src, new File(“screenshot.png”));
🔹 Q18: What Are Implicit, Explicit, and Fluent Waits in Selenium?
Answer:
- Implicit Wait: Applies globally to all elements.
- Explicit Wait: Waits for a specific condition.
- Fluent Wait: Custom polling & exception handling.
Java Code:
java
driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(15));
wait.until(ExpectedConditions.elementToBeClickable(By.id(“btn”)));
FluentWait<WebDriver> fluentWait = new FluentWait<>(driver)
.withTimeout(Duration.ofSeconds(20))
.pollingEvery(Duration.ofSeconds(2))
.ignoring(NoSuchElementException.class);
🔹 Q19: How to Remove Special Characters from a String in Java?
Answer:
Use regex to allow only alphanumerics.
Java Code:
java
String input = “Hello@#World123!”;
String clean = input.replaceAll(“[^a-zA-Z0-9]”, “”);
System.out.println(clean); // HelloWorld123
🔹 Q20: How to Split a String by Comma and Iterate?
Answer:
Use split() method and for-each loop.
Java Code:
java
String data = “apple,banana,grape”;
String[] fruits = data.split(“,”);
for (String fruit : fruits) {
System.out.println(fruit);
}
