java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal res

使用BigDecimal进行出发运算（调用divide()）时出现的，是因为不整除产生无先循环小数所致。源码如下：

 public BigDecimal divide(BigDecimal divisor) {
        BigInteger p = this.getUnscaledValue();
        BigInteger q = divisor.getUnscaledValue();
        BigInteger gcd; // greatest common divisor between 'p' and 'q'
        BigInteger quotAndRem[];
        long diffScale = (long)scale - divisor.scale;
        int newScale; // the new scale for final quotient
        int k; // number of factors "2" in 'q'
        int l = 0; // number of factors "5" in 'q'
        int i = 1;
        int lastPow = FIVE_POW.length - 1;

        if (divisor.isZero()) {
            throw new ArithmeticException("Division by zero");
        }
        if (p.signum() == 0) {
            return zeroScaledBy(diffScale);
        }
        // To divide both by the GCD
        gcd = p.gcd(q);
        p = p.divide(gcd);
        q = q.divide(gcd);
        // To simplify all "2" factors of q, dividing by 2^k
        k = q.getLowestSetBit();
        q = q.shiftRight(k);
        // To simplify all "5" factors of q, dividing by 5^l
        do {
            quotAndRem = q.divideAndRemainder(FIVE_POW[i]);
            if (quotAndRem[1].signum() == 0) {
                l += i;
                if (i < lastPow) {
                    i++;
                }
                q = quotAndRem[0];
            } else {
                if (i == 1) {
                    break;
                }
                i = 1;
            }
        } while (true);
        // If  abs(q) != 1  then the quotient is periodic
        if (!q.abs().equals(BigInteger.ONE)) {
        //异常信息
            throw new ArithmeticException("Non-terminating decimal expansion; no exact representable decimal result");
        }
        // The sign of the is fixed and the quotient will be saved in 'p'
        if (q.signum() < 0) {
            p = p.negate();
        }
        // Checking if the new scale is out of range
        newScale = safeLongToInt(diffScale + Math.max(k, l));
        // k >= 0  and  l >= 0  implies that  k - l  is in the 32-bit range
        i = k - l;

        p = (i > 0) ? Multiplication.multiplyByFivePow(p, i)
        : p.shiftLeft(-i);
        return new BigDecimal(p, newScale);
    }

解决方案：

使用三参数除法函数divide()，指定小数精确度。如：

new BigDecimal(mGypsumCountSum).divide(new BigDecimal(count),8,BigDecimal.ROUND_HALF_UP)

此处divide()的第二个参数是8表示小数精确8位。