Java MD5

Java 的MessageDigest 提供了生产MD5的算法，但是它返回的是byte[]，以下方法实现了MD5值为16进制字符串的返回值。
由于没有找到现成的转换方法，采用的是对每个字节比较来实现的.


public class MD5Security {
    private final static char[] hexDigits = { '0', '1', '2', '3', '4', '5',
            '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    private static String bytesToHex(byte[] bytes) {
        StringBuffer sb = new StringBuffer();
        int t;
        for (int i = 0; i < 16; i++) {// 16 == bytes.length;

            t = bytes[i];
            if (t < 0)
                t +=256;
            sb.append(hexDigits[(t >>> 4)]);
            sb.append(hexDigits[(t % 16)]);
        }
        return sb.toString();
    }

    public static String code(String input) throws Exception {
        try {
            MessageDigest md = MessageDigest.getInstance(System.getProperty(
                    "MD5.algorithm", "MD5"));
            return bytesToHex(md.digest(input.getBytes("utf-8")));

        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            throw new Exception("Could not found MD5 algorithm.", e);
        }
    }
}