HappyNumber.java

import java.util.ArrayList;

/**
 * This program calculates the first 8 happy numbers starting from a given
 * number.
 * 
 * Happy Number: http://en.wikipedia.org/wiki/Happy_number
 *
 * @author manojreddy
 *
 */
public class HappyNumber {

	public static boolean isHappy(int x){
		ArrayList<Integer> history = new ArrayList<Integer>();
		while(x!=1){
			history.add(x);
			
			int sum = 0;
			while(x!=0){
				sum+= Math.pow(x%10,2);
				x/=10;
			}
			
			x = sum;
			
			if(history.contains(x)){
				return false;
			}
			
		}
		
		return true;
		
	}

	//Assuming that "start" is a positive integer 
	public static void print8HappyNumbers(int start){
		int found = 0;

		while(found < 8){
			if(isHappy(start)){
				System.out.println(start);
				found++;
			}
			start++;
		}

	}

	public static void main(String[] args) {
		print8HappyNumbers(100);
	}
}