求指教Reterement中的代码

package SecondNight;
import java.util.*;
public class Reterement {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  Scanner  in=new Scanner(System.in);
  System.out.println("请输入你的年薪(payment)");
  double payment =in.nextDouble();
  System.out.println("请输入你的利息率");
  double interestRate=in.nextDouble();
  double  balance=0;
  int year=0;
  String input;
  //当用户没有退休时就更新账户
  do{
   // 添加这一年的平均年薪和利息率
   balance+=payment;
   double interest=balance*interestRate/100;
   balance+=interest;
   year++;
   //输出现在的收入
   System.out.printf("After year%d,your balance is %,.2f%n",year,balance);
   System.out.print("Ready to retire?(Y/N)");
   input=in.next();
   
  }
  while(input.equals("N"));
   

 }

}

 

 

 

 

 

 

这段代码中 System.out.printf("After year%d,your balance is %,.2f%n",year,balance);

 

我不明白，希望高手指教，