整数反转 https://leetcode-cn.com/problems/reverse-integer

gistfile1.txt

    /**
     * 整数反转
     * @param x 32位的整数
     * @return 如果超过最大最小限制，则返回0，否则返回反转之后的数字，符号位不变
     */
    private static int reverse(int x) {
        boolean negative = false;
        final int decimal = 10;
        final StringBuilder stringBuilder = new StringBuilder();

        if (x < 0) {
            x *= -1;
            negative = true;
        }


        for (int bitNum = x % decimal; x > 0; x = x / decimal, bitNum = x % decimal) {
            stringBuilder.append(bitNum);
        }

        final String result = stringBuilder.toString();

        if (result.isEmpty()) {
            return 0;
        }

        Long longValue = Long.valueOf(result);

        if (longValue > Integer.MAX_VALUE || longValue < Integer.MIN_VALUE) {
            return 0;
        }

        return (negative ? -1 : 1) * Integer.valueOf(result);
    }