输入一个数，如果各位数之和小于10，则输出位数之和，否则将位数之和继续求和，直到小于10，并输出

import java.io.BufferedInputStream;import java.util.Scanner;public class Main {public int digitalRoot(String s){int temp=0;for(int i=s.length()-1;i>=0;i--){temp+=(int)s.charAt(i)-(int)'0';}if(temp<=9){return temp;}while(temp>9){     int sum=0;while(temp/10>0){if(temp<100){sum=temp/10+temp%10;break;}int r=temp/10;sum+=temp%10;}temp=sum;}return temp;}public static void main(String[] args) {Scanner cin = new Scanner(new BufferedInputStream(System.in));String s = null;s = cin.next();System.out.println(new Main().digitalRoot(s));}}