Top 10 Java Coding Interview Questions

Here You Can See Top 10 Java Coding Interview Questions And Answers. Just Check It In Your IDE And Do Practice Of This Programming.

1) Reverse a String in Java ?

public class Main {
public static void main(String[] args) {
String input = “BoxofLearn”;
StringBuilder reversed = new StringBuilder(input).reverse();
System.out.println(reversed);
}
} Output : olleH

2) Check Prime Number ?

public class Main {
public static boolean isPrime(int n) {
if (n <= 1) return false;
for (int i = 2; i <= Math.sqrt(n); i++) {
if (n % i == 0) return false;
}
return true;
}
public static void main(String[] args) {
System.out.println(isPrime(29));
}
} Output : true

3) Find the Factorial of a Number ?

public class Main {
public static int factorial(int n) {
if (n == 0) return 1;
return n * factorial(n – 1);
}
public static void main(String[] args) {
System.out.println(factorial(5));
}
} Output : 120

4) Find the Largest Element in an Array ?

public class Main {
public static int findLargest(int[] arr) {
int max = arr[0];
for (int i = 1; i < arr.length; i++) { if (arr[i] > max)
max = arr[i];
}
return max;
}
public static void main(String[] args) {
int[] arr = {3, 7, 1, 9, 2};
System.out.println(findLargest(arr));
}
} Output : 9

5) Find the Second Largest Element in an Array ?

public class Main {
public static int secondLargest(int[] arr) {
int first = Integer.MIN_VALUE, second = Integer.MIN_VALUE;
for (int n : arr) {
if (n > first) {
second = first;
first = n;
} else if (n > second && n != first) {
second = n;
}
}
return second;
}
public static void main(String[] args) {
int[] arr = {3, 7, 1, 9, 2};
System.out.println(secondLargest(arr));
}
} Output : 7

6) Count Vowels in a String ?

public class Main {
public static int countVowels(String str) {
int count = 0;
for (char c : str.toLowerCase().toCharArray()) {
if (c == ‘a’ || c == ‘e’ || c == ‘i’ || c == ‘o’ || c == ‘u’)
count++;
}
return count;
}
public static void main(String[] args) {
System.out.println(countVowels(“Hello World”));
}
} Output : 3

7) Sum of Digits of a Number ?

public class Main {
public static int sumOfDigits(int n) {
int sum = 0;
while (n != 0) {
sum += n % 10;
n /= 10;
}
return sum;
}
public static void main(String[] args) {
System.out.println(sumOfDigits(1234));
}
} Output : 10

8) Find the Missing Number in an Array ?

public class Main {
public static int findMissing(int[] arr, int n) {
int sum = n * (n + 1) / 2;
for (int num : arr) sum -= num;
return sum;
}
public static void main(String[] args) {
int[] arr = {1, 2, 4, 5, 6};
System.out.println(findMissing(arr, 6));
}
} Output : 3

9) Find Duplicate Element in an Array ?

public class Main {
public static int findDuplicate(int[] arr) {
for (int i = 0; i < arr.length; i++) {
int index = Math.abs(arr[i]);
if (arr[index] < 0)
return index;
arr[index] = -arr[index];
}
return -1;
}
public static void main(String[] args) {
int[] arr = {1, 3, 4, 2, 2};
System.out.println(findDuplicate(arr));
}
} Output : 2

10) Merge Two Sorted Arrays

public class Main {
public static int[] mergeSortedArrays(int[] arr1, int[] arr2) {
int[] result = new int[arr1.length + arr2.length];
int i = 0, j = 0, k = 0;
while (i < arr1.length && j < arr2.length) {
if (arr1[i] < arr2[j])
result[k++] = arr1[i++];
else
result[k++] = arr2[j++];
}
while (i < arr1.length) result[k++] = arr1[i++];
while (j < arr2.length) result[k++] = arr2[j++];
return result;
}
public static void main(String[] args) {
int[] arr1 = {1, 3, 5};
int[] arr2 = {2, 4, 6};
int[] merged = mergeSortedArrays(arr1, arr2);
for (int n : merged)
System.out.print(n + ” “);
}
} Output : 1 2 3 4 5 6

This is Above Java Coding Interview Questions Most Asking In Interviews.