java中double四舍五入并设置小数点位数的问题

//方案一:
get_double = (double)(Math.round(result_value*100)/100.0) 

//方案二:
DecimalFormat df = new DecimalFormat("#.##");  
get_double = Double.ParseDouble(df.format(result_value));

//方案三:
get_double = Double.ParseDouble(String.format("%.2f",result_value));

//方案四:
BigDecimal bd = new BigDecimalresult_value();
BigDecimal  bd2 = bd.setScale(2,BigDecimal  .ROUND_HALF_UP);
get_double = Double.ParseDouble(bd2.ToString());

public static Double round(Double value, int scale) {
        double result = 0.0;
        if (null != value) {
            result = new BigDecimal(String.valueOf(value)).setScale(scale,RoundingMode.HALF_UP).doubleValue();
        }

        return result;

}