Java-小数点控制

package 运算及类型转换类;  

import java.text.DecimalFormat;  

public class 控制小数点类 {
     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;
        }
}