Java中如何取得指定小数位数的double型数据

1.使用NumberFormat

import   java.text.*;

public   class   FormatData   {

public   static   String   getResult(double   num)   {
                NumberFormat   format   =   NumberFormat.getNumberInstance();
                format.setMaximumFractionDigits(3);
return   format.format(num);
        }

public   static   void   main(String[]   args)   {
                System.out.println(getResult(0.0010));         }
} 

2.通过扩大后缩小的方法实现

public static double getDouble(int   n,double   a)
{
double   a2=a*n;
int   b=(int)a2;
double   c=(double)b;
double   d=c/n
return   d;
}