A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits in base-ten, and repeat the process until the number either equals 1 (where it will stay), or it loops endlessly in a cycle that does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers (or sad numbers)[1].
package education.jtrainer.ishappy;
public class IsHappy {
static int iteration=0;
static private Boolean isHappy(String a){
iteration++;
System.out.println("iteration n."+iteration+" input value:"+a);
int value=0;
int size=a.length();
int sum=0;
for (int i=0;i<size;i++) {
char element=a.charAt(i);
int valueInt=Character.getNumericValue(element);
sum=sum+valueInt*valueInt;
}
if (sum==1) return true;
else {
if (isUnHappy(sum)) return false;
return(isHappy(Integer.toString(sum)));
}
}
static private Boolean isUnHappy(int b){
Integer[] unhappylist = new Integer[]{4, 16, 37, 58, 89, 145, 42, 20};
for (int i=0;i<8;i++){
if (b==unhappylist[i]){
return true;
}
}
return false;
}
public static void main(String[] args) {
if (isHappy("49").equals(Boolean.TRUE)){
System.out.println("number is happy");
}
else {
System.out.println("number is unhappy");
}
}
}
Download from github:
https://github.com/jtrainer-education/HappyJava
References
[1] – https://en.wikipedia.org/wiki/Happy_number#cite_note-1
