java保留小数点后几位，不足的用0补

public class Test {
    public static void main(String[] args) {
       String result= Test.roundByScale(2.00,2);
        System.out.println(result);
    }
    public static String roundByScale(double v, int scale) {
        if (scale < 0) {
            throw new IllegalArgumentException(
                    "The   scale   must   be   a   positive   integer   or   zero");
        }
        if(scale == 0){
            return new DecimalFormat("0").format(v);
        }
        String formatStr = "0.";
        for(int i=0;i<scale;i++){
            formatStr = formatStr + "0";
        }
        return new DecimalFormat(formatStr).format(v);
    }
}