Java Program to Check Happy Number

Posted in Java Tutorial

Updated on Oct 30, 2024

By Mari Selvan

👁️ 128 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the domain of programming, certain mathematical properties and patterns are often explored. One such interesting concept is the notion of "happy numbers."

In this tutorial, we will delve into a Java program designed to determine whether a given number is a happy number.

📄 Example

Let's take a look at the Java code that checks whether a given number is a happy number or not.

HappyNumberChecker.java

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public class HappyNumberChecker {

// Function to calculate the sum of squares of digits
static int sumOfSquares(int n) {
  int sum = 0;
  while (n > 0) {
    int digit = n % 10;
    sum += digit * digit;
    n /= 10;
  }
  return sum;
}

// Function to check if a number is a happy number
static boolean isHappyNumber(int n) {
  int slow = n, fast = n;
  do {
    slow = sumOfSquares(slow);
    fast = sumOfSquares(sumOfSquares(fast));
  } while (slow != fast);

  return (slow == 1);
}

// Driver program
public static void main(String[] args) {
  // Replace this value with your desired number
  int number = 19;

  // Check if the number is a happy number
  if (isHappyNumber(number)) {
    System.out.println(number + " is a Happy Number.");
  } else {
    System.out.println(number + " is not a Happy Number.");
  }
}
}

💻 Testing the Program

To test the program with a different number, replace the value of number in the main method.

Output

19 is a Happy Number.

Compile and run the program to check if the number is a happy number.

🧠 How the Program Works

The program defines a class HappyNumberChecker containing a static method sumOfSquares to calculate the sum of the squares of digits.
It also defines a static method isHappyNumber that checks whether a given number is a happy number using Floyd's cycle detection algorithm.
The main method tests the program with a sample number (in this case, 19).

📏 Between the Given Range

Let's take a look at the java code that checks for Happy Numbers in the specified range.

HappyNumberChecker.java

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public class HappyNumberChecker {

  // Function to check if a number is happy
  static boolean isHappy(int n) {
    while (n != 1 && n != 4) {
      int sum = 0;
      while (n > 0) {
        int digit = n % 10;
        sum += digit * digit;
        n /= 10;
      }
      n = sum;
    }
    return n == 1;
  }

  // Driver program
  public static void main(String[] args) {
    // Define the range
    int start = 1;
    int end = 50;

    // Print the header
    System.out.println("Happy numbers in the range " + start + " to " + end + ":");

    // Check and print happy numbers in the range
    for (int i = start; i <= end; i++) {
      if (isHappy(i)) {
        System.out.print(i + " ");
      }
    }
  }
}

💻 Testing the Program

Output

Happy numbers in the range 1 to 50:
1 7 10 13 19 23 28 31 32 44 49

Compile and run the program to see the happy numbers within the specified range.

🧠 How the Program Works

The program defines a class HappyNumberChecker containing a static method isHappy to check if a number is happy.
Inside the main method, it specifies the range from 1 to 50.
It then checks each number in the range using the isHappy method and prints the happy numbers.

🧐 Understanding the Concept of Happy Number

A happy number is a positive integer defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1, or it loops endlessly in a cycle that does not include 1.

For example, let's take the number 19:

1²+9² = 82
8²+2² = 68
6²+8² = 100
1²+0²+0² = 1

In this case, 19 is a happy number because the process ends with 1.

🎢 Optimizing the Program

While the provided program is effective, there are various ways to optimize and enhance it further. Consider exploring different algorithms or incorporating additional features based on your specific requirements.

Feel free to incorporate and modify this code as needed for your specific use case. Happy coding!