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

 double a=saveNumber(15.12312312,6);
 System.out.println("a....."+a);
 }
 //保留小數(shù)點(diǎn)的位數(shù)
 //number為要處理的數(shù)，digit為要保留的位數(shù)
 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();

 
}
}