Java Coding Problems
Here are some basic Java coding problems that are commonly asked in interviews. Java coding problems cover a range of fundamental concepts like loops, conditionals, arrays, and string manipulation.
1. Check if a Number is Even or Odd
Output:
2. Find Factorial of a Number
import java.util.Scanner;
public class Factorial {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter a number: “);
int num = scanner.nextInt();
int factorial = 1;
for (int i = 1; i <= num; i++) {
factorial *= i;
}
System.out.println(“Factorial of ” + num + ” is ” + factorial);
scanner.close();
}
}
Example Input:
Output:
3. Check if a Number is Prime
import java.util.Scanner;
public class PrimeNumber {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter a number: “);
int num = scanner.nextInt();
boolean isPrime = true;
if (num <= 1) {
isPrime = false;
} else {
for (int i = 2; i <= Math.sqrt(num); i++) {
if (num % i == 0) {
isPrime = false;
break;
}
}
}
if (isPrime) {
System.out.println(num + ” is a prime number.”);
} else {
System.out.println(num + ” is not a prime number.”);
}
scanner.close();
}
}
Example Input:
Output:
4. Reverse a String
import java.util.Scanner;
public class ReverseString {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter a string: “);
String str = scanner.nextLine();
String reversed = “”;
for (int i = str.length() – 1; i >= 0; i–) {
reversed += str.charAt(i);
}
System.out.println(“Reversed string: ” + reversed);
scanner.close();
}
}
Example Input:
Output:
5. Find Largest of Three Numbers
import java.util.Scanner;
public class LargestNumber {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter first number: “);
int num1 = scanner.nextInt();
System.out.print(“Enter second number: “);
int num2 = scanner.nextInt();
System.out.print(“Enter third number: “);
int num3 = scanner.nextInt();
if (num1 >= num2 && num1 >= num3) {
System.out.println(num1 + ” is the largest number.”);
} else if (num2 >= num1 && num2 >= num3) {
System.out.println(num2 + ” is the largest number.”);
} else {
System.out.println(num3 + ” is the largest number.”);
}
scanner.close();
}
}
Example Input:
Output:
6. Sum of Digits of a Number
import java.util.Scanner;
public class SumOfDigits {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter a number: “);
int num = scanner.nextInt();
int sum = 0;
while (num != 0) {
sum += num % 10;
num /= 10;
}
System.out.println(“Sum of digits: ” + sum);
scanner.close();
}
}
Example Input:
Output:
7. Fibonacci Series
import java.util.Scanner;
public class Fibonacci {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter the number of terms: “);
int terms = scanner.nextInt();
int first = 0, second = 1;
System.out.print(“Fibonacci Series: “);
for (int i = 1; i <= terms; i++) {
System.out.print(first + ” “);
int next = first + second;
first = second;
second = next;
}
scanner.close();
}
}
Example Input:
Output:
8. Palindrome Check
import java.util.Scanner;
public class Palindrome {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter a string: “);
String str = scanner.nextLine();
String reversed = “”;
for (int i = str.length() – 1; i >= 0; i–) {
reversed += str.charAt(i);
}
if (str.equals(reversed)) {
System.out.println(str + ” is a palindrome.”);
} else {
System.out.println(str + ” is not a palindrome.”);
}
scanner.close();
}
}
Example Input:
Output:
9. Count Vowels and Consonants in a String
import java.util.Scanner;
public class VowelConsonant {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter a string: “);
String str = scanner.nextLine().toLowerCase();
int vowels = 0, consonants = 0;
for (int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
if (ch >= ‘a’ && ch <= ‘z’) {
if (ch == ‘a’ || ch == ‘e’ || ch == ‘i’ || ch == ‘o’ || ch == ‘u’) {
vowels++;
} else {
consonants++;
}
}
}
System.out.println(“Vowels: ” + vowels);
System.out.println(“Consonants: ” + consonants);
scanner.close();
}
}
Example Input:
Output:
10. Find GCD (Greatest Common Divisor)
import java.util.Scanner;
public class GCD {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter first number: “);
int num1 = scanner.nextInt();
System.out.print(“Enter second number: “);
int num2 = scanner.nextInt();
while (num1 != num2) {
if (num1 > num2) {
num1 -= num2;
} else {
num2 -= num1;
}
}
System.out.println(“GCD: ” + num1);
scanner.close();
}
}
Example Input:
Output: