pocky问题 哪位大神帮我解释一下

import java.util.Scanner;  public class mazi { public static void main(String[] args) {
  Scanner sc =new Scanner(System.in);  int T=sc.nextInt();  while (T-- >0){ double n = sc.nextDouble();  double m =sc.nextDouble();  if(n<=m)
      System.out.println("0.000000");  else  System.out.printf("%.6f\n",1+ Math.log(n/m));//printf为什么不行  // System.out.printf("%.6f\n", 1 + Math.log(n / m));  }
    }}