soddr_my.java

public static int digital_root(int n) {
	int sum = 0;
		
	if(String.valueOf(n).length() == 1){
		return n;
	}
		
	while(String.valueOf(n).length() != 1){
		sum += n % 10;
		n = n / 10;
	}
		
	sum += n;
		
	if(String.valueOf(sum).length() == 1){
		return sum;
	}else{
		return digital_root(sum);
	}
}