BigDecimal bd = new BigDecimal(0.0199999999999);

System.out.println("res:"+bd.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue());

         DecimalFormat df = new DecimalFormat("#.00");

         System.out.println(df.format(Double.parseDouble(str)));

         System.out.println("=================");

         System.out.println(String.format("%.2f", Double.parseDouble(str)));

         System.out.println("=================");

         NumberFormat nf = NumberFormat.getNumberInstance();

         nf.setMaximumFractionDigits(2);

         System.out.println(nf.format(Double.parseDouble(str)));