decode md5 ecnrytion in java
<pre><code>public static String convertToMD5(String input) throws Exception {
    String md5 = null;
    if (null == input)
        return null;
    try {
        // Create MessageDigest object for MD5
        MessageDigest digest = MessageDigest.getInstance("MD5");
        // Update input string in message digest
        digest.update(input.getBytes(), 0, input.length());
        // Converts message digest value in base 16 (hex)
        md5 = new BigInteger(1, digest.digest()).toString(16);
    } catch (NoSuchAlgorithmException e) {

        throw e;
    }
    return md5;
}
</code></pre>

<p>using this code to encrypt the string 
i want to decode md5 encryption to normal string?
can you help</p>