java中String编码转换 UTF-8转GBK

1.GB2312等都可以用GBK代替.
2.new String(row.getBytes("GB2312"), "UTF8")  这种写法是不对的, 中文仍然会乱码.

方案:
解决GBK字符转UTF-8乱码问题: https://www.cnblogs.com/xijin-wu/p/5884822.html

   彻底搞懂编码 GBK 和 UTF8:https://www.cnblogs.com/hehheai/p/6510879.html

/**
     * GBK转UTF-8
     * @param gbkStr
     * @return
     */
    public static byte[] getUTF8BytesFromGBKString(String gbkStr) {
        int n = gbkStr.length();
        byte[] utfBytes = new byte[3 * n];
        int k = 0;
        for (int i = 0; i < n; i++) {
            int m = gbkStr.charAt(i);
            if (m < 128 && m >= 0) {
                utfBytes[k++] = (byte) m;
                continue;
            }
            utfBytes[k++] = (byte) (0xe0 | (m >> 12));
            utfBytes[k++] = (byte) (0x80 | ((m >> 6) & 0x3f));
            utfBytes[k++] = (byte) (0x80 | (m & 0x3f));
        }
        if (k < utfBytes.length) {
            byte[] tmp = new byte[k];
            System.arraycopy(utfBytes, 0, tmp, 0, k);
            return tmp;
        }
        return utfBytes;
    }