Java控制小数点的几个常用方法

import java.text.DecimalFormat;public class NumberUtil {        public static double decimalFormatD(int num, double d){        String format = "0.";        String result = "";        double db;                for(int i=0;i<num;i++)            format = format.concat("0");                DecimalFormat decimal = new DecimalFormat(format);        result = decimal.format(d);        db = Double.parseDouble(result);                return db;    }        public static float decimalFormatF(int num, float f){        String format = "0.";        String result = "";        float fl;                for(int i=0;i<num;i++)            format = format.concat("0");                DecimalFormat decimal = new DecimalFormat(format);        result = decimal.format(f);        fl = Float.parseFloat(result);                return fl;    }        public static String doubleToString(double f){               String s = "";        double a = 0;                while(f >= 1) {                        a = f%((double)10);                        s = String.valueOf((int)a) + s;            f=(f - a)/10;        }        return s;    }}