帮我解释解释
import java.util.Scanner; public class taShiJiWeiShu { public static void main(String[] args) { @SuppressWarnings("resource") Scanner in = new Scanner(System.in); int num = in.nextInt(); int amount = 0; do { num = num / 10; amount++; }while(num > 0); System.out.println("它是个"+amount+"位数"); } }