In the previous article, we have discussed Java Program to Check Duck Number

In this article we are going to understand what Happy number is and how we can check whether a number is Happy or not in Java with examples.

## Java Program to Check Happy Number

**Happy numbers** are numbers which eventually reach 1 when replaced by the sum of the square of each digit. Those numbers that do not reach 1 are unhappy numbers (or here not happy numbers).

Example: 23 -> Happy number 133 -> Happy number 9 -> Not a Happy number

In the above examples the numbers 23 and 133 both are happy numbers while 9 is not.

Let’s see different ways to do it.

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**Approach:**

- We ask the user to enter a number which we store in an integer variable
`num`

. - We then use a while loop to iterate digits in the number and calculate the sum of their square.
- After coming out of loop if the resultant sum is 1 then the number is a happy number, else it is not.

### Method-1:Java Program to Check Happy Number By Using Static Value

import java.util.Scanner; public class HappyNumber { public static void main(String args[]) { // A number is declared int num = 23; //Temp is used to preserve the original value int temp = num,sum = 0, remainder =1; //Loop to add the digits while (temp > 9) { //Loop to iterate the digits while (temp > 0) { remainder = temp % 10; sum = sum + (remainder * remainder); temp = temp / 10; } temp = sum; sum = 0; } if (temp == 1) { System.out.println(num+" is a Happy Number"); } else { System.out.println(num+" is Not a Happy Number"); } } }

Output: 23 is a Happy Number

### Method-2:By Using User Input Value

import java.util.Scanner; public class HappyNumber { public static void main(String args[]) { //Taking the number as input from the user using scanner class Scanner scan = new Scanner(System.in); System.out.print("Enter a number : "); int num = scan.nextInt(); //Temp is used to preserve the original value int temp = num,sum = 0, remainder =1; //Loop to add the digits while (temp > 9) { //Loop to iterate the digits while (temp > 0) { remainder = temp % 10; sum = sum + (remainder * remainder); temp = temp / 10; } temp = sum; sum = 0; } if (temp == 1) { System.out.println(num+" is a Happy Number"); } else { System.out.println(num+" is Not a Happy Number"); } } }

Output: Enter a number : 23 23 is a Happy Number

### Method-3:Java Program to Check Happy Number By Using User Defined Method

import java.util.Scanner; public class HappyNumber { public static void main(String args[]) { //Taking the number as input from the user using scanner class Scanner scan = new Scanner(System.in); System.out.print("Enter a number : "); int num = scan.nextInt(); //calling checkNumber() user defined method //to check the number is happy number or not. checkNumber(num); } public static void checkNumber(int num) { //Temp is used to preserve the original value int temp = num,sum = 0, remainder =1; //Loop to add the digits while (temp > 9) { //Loop to iterate the digits while (temp > 0) { remainder = temp % 10; sum = sum + (remainder * remainder); temp = temp / 10; } temp = sum; sum = 0; } if (temp == 1) { System.out.println(num+" is a Happy Number"); } else { System.out.println(num+" is Not a Happy Number"); } } }

Output: Enter a number : 23 23 is a Happy Number

Guys who are serious about learning the concepts of the java programming language should practice this list of programs in java and get a good grip on it for better results in exams or interviews.

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