How to convert Object to String in J2ME for Nokia Asha?

I'm developing for Nokia Asha and using Tantalum library to make my HTTP requests through the HTTPPoster class.

When the task is executed I try to get the value from the X-Session-Id header from the rest of the response headers, these are returned as a HashTable, the value in this header I need to convert it to a SHA256 hash.

But I am unable to convert the value I get from the HashTable into String.

My code looks like this:

final HttpPoster httpPoster = new HttpPoster(Task.FASTLANE_PRIORITY, completeURL);
        httpPoster.setRequestProperty("Content-Type", "application/json");
        httpPoster.setPostData(new byte[]{});
        httpPoster.chain(new Task(Task.FASTLANE_PRIORITY){

            protected Object exec(Object in) throws CancellationException,
                    TimeoutException, InterruptedException {
                // TODO Auto-generated method stub
                System.out.println("Task is executing");

                String tmpSessionId = new String(httpPoster.getResponseHeaders().get("X-Session-Id").toString().getBytes());

                byte[] input = null;
                try {
                    input = new String("X-Session-Sig" + tmpSessionId + "test").getBytes("UTF-8");
                } catch (UnsupportedEncodingException e) {
                    // TODO Auto-generated catch block
                    System.out.println("Unsupported encoding exception");
                    e.printStackTrace();
                }

                byte[] key = new byte[4];
                int tmpInt = new Random().nextInt();
                key[0] = (byte)(tmpInt >> 24);
                key[1] = (byte)(tmpInt >> 16);
                key[2] = (byte)(tmpInt >> 8);
                key[3] = (byte)(tmpInt);


                Digest digest = new SHA256Digest();
                HMac hmac = new HMac(digest);
                hmac.init(new KeyParameter(key));
                hmac.update(input, 0, input.length);
                byte[] output = new byte[digest.getDigestSize()];
                hmac.doFinal(output, 0);
                sessionId = tmpSessionId;
                sessionSig = new String(Hex.encode(output));
                System.out.println("session id " + sessionId + " session signature " + sessionSig);
                return in;
            }
            protected void onCanceled(){
                System.out.println("Request was cancelled");
            }
        });
        httpPoster.fork();

As you can see, in the line String tmpSessionId = new String(httpPoster.getResponseHeaders().get("X-Session-Id").toString().getBytes()); I try to convert to String and then get the bytes but this returns [Ljava.lang.String;@6f7159d, not the actual value I'm looking for, even calling the method toString() without performing the getBytes method returns the same value.

How can I get the true value of this element in the HashTable? As far as I can see, J2ME doesn't support ObjectOutputStream class. What are the alternatives?

I found that the [Ljava.lang.String;@6f7159d part meant that the object inside the HashTable was a String array.

After realizing that I just need to cast to String[]:

String[] stringArray = (String[]) dotREZApi.getCurrentRequest().getResponseHeaders().get("X-Session-Id");
String tmpSessionId = stringArray[0];

This returned to me the value I was expecting.