💻 Java Interview Questions and Answers (Part 4 – Practical Coding & Programs)
Coding questions are the heart of any Java interview.
Even if you understand all the theory, you must know how to write small working programs that show your problem-solving skills.
Let’s go through 30+ most asked Java coding questions with easy explanations and outputs 👇
🔹 1. Write a program to print “Hello World” in Java.
Answer:
class Hello {
public static void main(String[] args) {
System.out.println("Hello World");
}
}
✅ Output: Hello World
👉 This is the simplest Java program that every beginner starts with.
🔹 2. Write a program to find the sum of two numbers.
class Sum {
public static void main(String[] args) {
int a = 10, b = 20;
int sum = a + b;
System.out.println("Sum: " + sum);
}
}
✅ Output: Sum: 30
🔹 3. Write a program to check if a number is even or odd.
class EvenOdd {
public static void main(String[] args) {
int num = 5;
if(num % 2 == 0)
System.out.println("Even");
else
System.out.println("Odd");
}
}
✅ Output: Odd
🔹 4. Program to find the largest of three numbers.
class Largest {
public static void main(String[] args) {
int a = 10, b = 25, c = 15;
if(a >= b && a >= c)
System.out.println(a + " is largest");
else if(b >= a && b >= c)
System.out.println(b + " is largest");
else
System.out.println(c + " is largest");
}
}
✅ Output: 25 is largest
🔹 5. Program to check if a number is prime.
class Prime {
public static void main(String[] args) {
int num = 7;
boolean flag = true;
for(int i = 2; i <= num/2; i++) {
if(num % i == 0) {
flag = false;
break;
}
}
if(flag)
System.out.println(num + " is prime");
else
System.out.println(num + " is not prime");
}
}
✅ Output: 7 is prime
🔹 6. Program to reverse a number.
class ReverseNumber {
public static void main(String[] args) {
int num = 1234, rev = 0;
while(num != 0) {
rev = rev * 10 + num % 10;
num = num / 10;
}
System.out.println("Reversed: " + rev);
}
}
✅ Output: Reversed: 4321
🔹 7. Program to check if a number is palindrome.
class Palindrome {
public static void main(String[] args) {
int num = 121, original = num, rev = 0;
while(num != 0) {
rev = rev * 10 + num % 10;
num = num / 10;
}
if(original == rev)
System.out.println("Palindrome");
else
System.out.println("Not Palindrome");
}
}
✅ Output: Palindrome
🔹 8. Program to find factorial of a number.
class Factorial {
public static void main(String[] args) {
int num = 5;
int fact = 1;
for(int i = 1; i <= num; i++) {
fact *= i;
}
System.out.println("Factorial: " + fact);
}
}
✅ Output: Factorial: 120
🔹 9. Program to find Fibonacci series up to n terms.
class Fibonacci {
public static void main(String[] args) {
int n = 7, a = 0, b = 1;
System.out.print(a + " " + b);
for(int i = 2; i < n; i++) {
int c = a + b;
System.out.print(" " + c);
a = b;
b = c;
}
}
}
✅ Output: 0 1 1 2 3 5 8
🔹 10. Program to find sum of digits of a number.
class SumOfDigits {
public static void main(String[] args) {
int num = 123, sum = 0;
while(num > 0) {
sum += num % 10;
num /= 10;
}
System.out.println("Sum of digits: " + sum);
}
}
✅ Output: Sum of digits: 6
🔹 11. Program to swap two numbers without using third variable.
class Swap {
public static void main(String[] args) {
int a = 10, b = 20;
a = a + b;
b = a - b;
a = a - b;
System.out.println("a: " + a + ", b: " + b);
}
}
✅ Output: a: 20, b: 10
🔹 12. Program to check if a string is palindrome.
class StringPalindrome {
public static void main(String[] args) {
String str = "madam";
String rev = new StringBuilder(str).reverse().toString();
if(str.equals(rev))
System.out.println("Palindrome String");
else
System.out.println("Not Palindrome");
}
}
✅ Output: Palindrome String
🔹 13. Program to count vowels and consonants in a string.
class CountVowels {
public static void main(String[] args) {
String str = "Hello Java";
int vowels = 0, consonants = 0;
str = str.toLowerCase();
for(char c : str.toCharArray()) {
if("aeiou".indexOf(c) != -1)
vowels++;
else if(Character.isLetter(c))
consonants++;
}
System.out.println("Vowels: " + vowels);
System.out.println("Consonants: " + consonants);
}
}
✅ Output:
Vowels: 4
Consonants: 4
🔹 14. Program to reverse a string.
class ReverseString {
public static void main(String[] args) {
String str = "Java";
String rev = "";
for(int i = str.length() - 1; i >= 0; i--) {
rev += str.charAt(i);
}
System.out.println("Reversed: " + rev);
}
}
✅ Output: Reversed: avaJ
🔹 15. Program to find largest element in an array.
class LargestArray {
public static void main(String[] args) {
int arr[] = {10, 25, 3, 50, 2};
int max = arr[0];
for(int n : arr) {
if(n > max)
max = n;
}
System.out.println("Largest: " + max);
}
}
✅ Output: Largest: 50
🔹 16. Program to sort an array in ascending order.
import java.util.Arrays;
class SortArray {
public static void main(String[] args) {
int arr[] = {5, 1, 4, 2, 3};
Arrays.sort(arr);
System.out.println(Arrays.toString(arr));
}
}
✅ Output: [1, 2, 3, 4, 5]
🔹 17. Program to find second largest element in an array.
import java.util.Arrays;
class SecondLargest {
public static void main(String[] args) {
int arr[] = {12, 35, 1, 10, 34, 1};
Arrays.sort(arr);
System.out.println("Second Largest: " + arr[arr.length - 2]);
}
}
✅ Output: Second Largest: 34
🔹 18. Program to check Armstrong number.
class Armstrong {
public static void main(String[] args) {
int num = 153, temp = num, sum = 0;
while(num != 0) {
int digit = num % 10;
sum += digit * digit * digit;
num /= 10;
}
if(sum == temp)
System.out.println("Armstrong Number");
else
System.out.println("Not Armstrong");
}
}
✅ Output: Armstrong Number
🔹 19. Program to find duplicate elements in an array.
class Duplicate {
public static void main(String[] args) {
int arr[] = {1, 2, 3, 2, 4, 1};
for(int i = 0; i < arr.length; i++) {
for(int j = i + 1; j < arr.length; j++) {
if(arr[i] == arr[j])
System.out.println("Duplicate: " + arr[j]);
}
}
}
}
✅ Output:
Duplicate: 2
Duplicate: 1
🔹 20. Program to count words in a string.
class CountWords {
public static void main(String[] args) {
String str = "Java is fun to learn";
String[] words = str.split(" ");
System.out.println("Word Count: " + words.length);
}
}
✅ Output: Word Count: 5
🔹 21. Program to find factorial using recursion.
class FactorialRec {
static int fact(int n) {
if(n == 1)
return 1;
else
return n * fact(n - 1);
}
public static void main(String[] args) {
System.out.println("Factorial: " + fact(5));
}
}
✅ Output: Factorial: 120
🔹 22. Program to check leap year.
class LeapYear {
public static void main(String[] args) {
int year = 2024;
if((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
System.out.println("Leap Year");
else
System.out.println("Not Leap Year");
}
}
✅ Output: Leap Year
🔹 23. Program to count number of digits in a number.
class CountDigits {
public static void main(String[] args) {
int num = 12345, count = 0;
while(num != 0) {
num = num / 10;
count++;
}
System.out.println("Digits: " + count);
}
}
✅ Output: Digits: 5
🔹 24. Program to find smallest element in an array.
class Smallest {
public static void main(String[] args) {
int arr[] = {10, 2, 8, 3};
int min = arr[0];
for(int n : arr) {
if(n < min)
min = n;
}
System.out.println("Smallest: " + min);
}
}
✅ Output: Smallest: 2
🔹 25. Program to print multiplication table.
class Table {
public static void main(String[] args) {
int num = 5;
for(int i = 1; i <= 10; i++)
System.out.println(num + " x " + i + " = " + (num * i));
}
}
✅ Output:
5 x 1 = 5
5 x 2 = 10
…
5 x 10 = 50
🔹 26. Program to check if a character is vowel or consonant.
class VowelCheck {
public static void main(String[] args) {
char c = 'e';
if("aeiouAEIOU".indexOf(c) != -1)
System.out.println("Vowel");
else
System.out.println("Consonant");
}
}
✅ Output: Vowel
🔹 27. Program to convert string to character array.
class ToCharArray {
public static void main(String[] args) {
String str = "Java";
char[] arr = str.toCharArray();
for(char c : arr)
System.out.print(c + " ");
}
}
✅ Output: J a v a
🔹 28. Program to find sum of elements in an array.
class SumArray {
public static void main(String[] args) {
int arr[] = {1, 2, 3, 4, 5};
int sum = 0;
for(int n : arr)
sum += n;
System.out.println("Sum: " + sum);
}
}
✅ Output: Sum: 15
🔹 29. Program to check if a number is perfect.
class PerfectNumber {
public static void main(String[] args) {
int num = 28, sum = 0;
for(int i = 1; i < num; i++) {
if(num % i == 0)
sum += i;
}
if(sum == num)
System.out.println("Perfect Number");
else
System.out.println("Not Perfect");
}
}
✅ Output: Perfect Number
🔹 30. Program to find power of a number.
class Power {
public static void main(String[] args) {
int base = 2, exp = 3, result = 1;
for(int i = 1; i <= exp; i++) {
result *= base;
}
System.out.println("Power: " + result);
}
}
✅ Output: Power: 8
🟢 Final Tips for Coding Rounds
- Always write clean and readable code.
- Try to explain your logic step-by-step to the interviewer.
- Use
forandwhileloops confidently. - Learn small string and array tricks — they appear often!
- Practice on platforms like LeetCode, HackerRank, or CodeStudio.