Android : Parse query.whereEqualTo String issue

I am using Parse backend for my android app. I need to query the database for a record that has a field with a specific string value. following is the Parse code

strObjectId is a String initialised with a Parse ObjectId as follows

        String strObjectId = MyParseObject.getObjectId();

Parse code

        ParseQuery<ParseObject> query = ParseQuery.getQuery("MyDataTable");
        query.whereEqualTo("code", Code);
        query.getFirstInBackground(new GetCallback<ParseObject>()
        {
          public void done(ParseObject object, ParseException e)
          {
            if (object == null) 
            {
                return;
            } 
            else 
            {
                ShowToast("Record found!");
            }
          }
        });

The problem is that it works perfectly okay when 'Code' is hardcoded as follows prior to running above query

        String Code = "KrErdfgdfghdfh";

But it DOES NOT work when Code is assigned Parse ObjectId as follows

        String Code = strObjectId;

Your help will be appreciated

Thanks