MD5 加密

public class MD5 {
    /**
     * MD5 字符串加密
     *
     * @param plainText     待加密字符串
     * @param num           加密位数
     * @return              加密后字符串
     */
    public static String md5(String plainText, int num) throws NoSuchAlgorithmException {

        MessageDigest md = MessageDigest.getInstance("MD5");
        md.update(plainText.getBytes());
        byte b[] = md.digest();
        int i;
        StringBuilder buf = new StringBuilder("");
        for (byte aB : b) {
            i = aB;
            if (i < 0)
                i += 256;
            if (i < 16)
                buf.append("0");
            buf.append(Integer.toHexString(i));
        }

        if (num == 32) {
            return buf.toString().toUpperCase();
        }

        return buf.toString().substring(8, 24).toUpperCase();

    }

    /**
     * MD5 字符串加密
     *
     * @param plainText     待加密字符串
     * @return              加密后字符串
     */
    public static String md5(String plainText) {
        String passwd = "";
        try {
            passwd =  md5(plainText, 32);
        } catch (Exception e) {

        }
        return passwd;
    }

}