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Java program to print happy numbers for a given range

This is a Java program to print happy numbers for a given range. But what is a happy number?

A number whose sum of the square of digits is ultimatly equal to 1 is a happy number. By ultimately we mean that starting with any positive number we continue the addition of square of digits till we get a single digit number (0 ~ 9). But the on whose sum is ultimately 1 is a happy number.

Example #1: 13 ; 12 + 32 = 1 + 9 =10 ; 1 2 + 0 2 = 1 (Thus a happy number)
Example #2: 32; 3 2 + 2 2 = 9 + 4 = 13; and in Example#1 13 is already a happy number;
Some of the first happy numbers (upto 150) are: 1, 7, 10, 13, 19, 23, 28, 31, 32, 44, 49, 68, 70, 79, 82, 86, 91, 94, 97, 100, 103, 109, 129, 130.

ALSO CHECK : Java program to check for a happy number

import java.io.*;
class happynumber
{
public static void main(String args[])throws Exception
{
int i,j,n,k;
happynumber obj=new happynumber();
System.out.print("Enter the upper limit for happy number series : ");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
n=Integer.parseInt(br.readLine());           // Accept the range for the happy numbers till n i.e happy numbers from 1 to n
for(k=0;k<n;k++)
{i=k;
	while((j= obj.happy(i))/10 !=0)       //   You have to check the sum of all digits until a single digit is achieved i.e. sum=1,2,3,..9
	{
	i=j;				// If sum of digits= 19 it then again goes to 1+9 =10 and again 1+0= '1' a single digit to check if 1 or not
	}
	if(j==1)
System.out.print(k+",");
}
}
int happy (int n)
{
if(n/10==0)
return n*n;
else
return (int)Math.pow(n%10,2)+ happy(n/10);
}
}

OUTPUT:

Java program to print happy number series
Java program to print happy number series

Incoming terms: Java program to print happy numbers for a given range, program for happy number series

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