题解 | #数列求和#

import java.util.StringJoiner;

public class Main {
    public static void main(String[] args) {

        //write your code here........
        StringJoiner joiner = new StringJoiner(",");
        String a = "";
        long total = 0L;
        for (long i = 1; i <= 10; i++) {
            a = "9" + a;
            joiner.add(a);
            //计算
            total = total + Long.valueOf(a);
        }
        //System.out.println(joiner.toString());
        System.out.println(total);

    }
}