Top 10 Java Coding Interview Programs (With Solutions)

These are the most frequently asked Java coding questions in interviews for freshers and beginners.

If you're preparing for Java interviews, solving coding programs is just as important as learning theory.

When I started practicing Java, I realized that interviewers often ask simple coding questions to test logic, syntax, and problem-solving ability.

Written by Shivkumar Udas – Engineering student sharing practical Java guides for beginners.

💡 Why Coding Questions Matter

Many Java interviews include small coding problems to test how well you understand loops, conditions, and logic building.

1. Java Program to Print Hello World

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

Time Complexity: O(1)

2. Java Program to Check Even or Odd

int number = 10;

if(number % 2 == 0){
    System.out.println("Even");
}else{
    System.out.println("Odd");
}

Time Complexity: O(1)

Interview Variation: Check even/odd without using modulus operator.

3. Java Program to Find Largest of Three Numbers

int a = 10, b = 25, c = 15;

if(a >= b && a >= c){
    System.out.println(a);
}else if(b >= a && b >= c){
    System.out.println(b);
}else{
    System.out.println(c);
}

Time Complexity: O(1)

4. Java Program to Reverse a Number

int number = 1234;
int reverse = 0;

while(number != 0){
    int digit = number % 10;
    reverse = reverse * 10 + digit;
    number = number / 10;
}

System.out.println(reverse);

Time Complexity: O(n)

Interview Variation: Reverse using recursion.

5. Java Program to Check Palindrome Number

int number = 121;
int original = number;
int reverse = 0;

while(number != 0){
    int digit = number % 10;
    reverse = reverse * 10 + digit;
    number = number / 10;
}

if(original == reverse){
    System.out.println("Palindrome");
}else{
    System.out.println("Not Palindrome");
}

Time Complexity: O(n)

6. Java Program to Print Fibonacci Series

int n = 10, first = 0, second = 1;

for(int i = 2; i < n; i++){
    int next = first + second;
    System.out.print(next + " ");
    first = second;
    second = next;
}

Time Complexity: O(n)

7. Java Program to Check Prime Number

int number = 13;
boolean isPrime = true;

for(int i = 2; i <= number/2; i++){
    if(number % i == 0){
        isPrime = false;
        break;
    }
}

if(isPrime && number > 1){
    System.out.println("Prime");
}else{
    System.out.println("Not Prime");
}

Time Complexity: O(n)

Interview Variation: Optimize using square root method.

8. Java Program to Find Factorial

int number = 5;
int factorial = 1;

for(int i = 1; i <= number; i++){
    factorial *= i;
}

System.out.println(factorial);

Time Complexity: O(n)

9. Java Program to Swap Two Numbers

int a = 5, b = 10;

int temp = a;
a = b;
b = temp;

System.out.println(a + " " + b);

Time Complexity: O(1)

Interview Variation: Swap without using a third variable.

10. Java Program to Count Digits

int number = 12345;
int count = 0;

while(number != 0){
    number = number / 10;
    count++;
}

System.out.println(count);

Time Complexity: O(n)

📌 Most Important Programs to Practice

• Prime Number
• Palindrome
• Fibonacci
• Factorial
• Reverse Number

🎯 Interview Tip

Do not memorize code. Practice writing logic step by step.

In interviews, your explanation matters more than the code itself.

🔗 Related Guides

• Java Interview Questions
• Java Collections Framework

🎯 Conclusion

Practicing these programs will improve your logic and confidence.

Start with basics and gradually move to advanced problems.