//四舍五入

    public static double toDecimal(Double num){

        if(Double.isNaN(num) || num == null){

            return 0;

        }

        return new BigDecimal(num).setScale(2, RoundingMode.HALF_UP).doubleValue();

    }

    /**

     * 两个double相除

     * @param v1

     * @param v2

     * @param scale

     * @return

     */

    public static double division(double v1, double v2, int scale) {

        if (scale < 0) {

            throw new IllegalArgumentException(

                    "The scale must be a positive integer or zero");

        }

        BigDecimal b1 = new BigDecimal(Double.toString(v1));

        BigDecimal b2 = new BigDecimal(Double.toString(v2));

        return b1.divide(b2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();

    }

    /**

     * 两个Double数相加

     * @param v1

     * @param v2

     * @return Double

     */

    public static Double add (Double v1,Double v2){

        BigDecimal b1 = new BigDecimal(v1.toString());

        BigDecimal b2 = new BigDecimal(v2.toString());

        return b1.add(b2).doubleValue();

    }

    /**

      * 两个Double数相减

      * @param v1

      * @param v2

      * @return Double

      */

    public static Double sub(Double v1,Double v2){

        BigDecimal b1 = new BigDecimal(v1.toString());

        BigDecimal b2 = new BigDecimal(v2.toString());

        return b1.subtract(b2).doubleValue();

    }

    /**

     * 两个Double数相乘

     * @param v1

     * @param v2

     * @return Double

     */

    public static Double mul(Double v1,Double v2){

        BigDecimal b1 = new BigDecimal(v1.toString());

        BigDecimal b2 = new BigDecimal(v2.toString());

        return b1.multiply(b2).doubleValue();

    }