Use Java code to preserve the number of decimal places

import java.text.* ; 
import java.math.* ; 
public class Test
{ 
 public Test(){

 double a=saveNumber(15.12312312,6);
 System.out.println("a....."+a);
 }
 //Reserve the number of decimal places
 //Number is the number to be processed, and digit is the number to be reserved
 public double  saveNumber(double number,int digit){

 NumberFormat ddf1=NumberFormat.getNumberInstance();

 ddf1.setMaximumFractionDigits(digit); 

 String s= ddf1.format(number);

 double  Num=Double.parseDouble(s);

 return Num;

 }
public static void main(String args[]) 
{ 
 new Test();

 
} 
}