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());