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Hashtable Keys not responding

Posted on 2003-03-08
Medium Priority
Last Modified: 2010-03-31

I cant seem to read the values from the Hashtable in this program. The programs reads a txt file that looks like this

User-Agent : HertsWeb/1.0
Accept-Language : en
Accept : text/plain
Accept : application/x-html
Accept : application/html

Everything is read into a HashTable. But i cant seem to read any value from it as it returns null, i think the problem is the value i am assigning to the key.. e.g. theDetails.get(String new("User-Agent"))

        public BrowserDetails()
              // Initialise all valus to null
              theDetails = null;
              inStream = null;
              outStream = null;
              // Create the details hashtable
              theDetails = new Hashtable();
              // Get and set contents of the file
      * Private Methods                                                                                            *
      // Method reads the contents of the file and stores each value no the
      // Hashtable
      private void readBrowserDetails()
                  // Set up the input stream for reading
                  inStream = new FileInputStream(browserFile);
                  // Set up the input stream for reading one line at a time
                  fileInput = new BufferedReader(new InputStreamReader(inStream));
                  // While there is something to read
                  for (i=0; (tempStorage=fileInput.readLine()) != null;i++)
                        // Create a tokenise with what was just read
                        StringTokenizer tokenizer = new StringTokenizer(tempStorage, ":");
                        //Separate the string in the form string1 string2 string3
                        //We only need string1 and string3 threfore we will discards string 2
                        String tempKey = new String();
                        String tempValue = new String();
                        int index = 1;
                        // Get three tokens from the string
                        while (tokenizer.hasMoreTokens())
                              tempKey = tokenizer.nextToken().toString();
                              tempValue = tokenizer.nextToken();
                              theDetails.put(new String(tempKey),new String(tempValue));
                        }// while has more tokens
                        //Put current Element into hashtable
                   }// for index=0
                   System.out.println("---------- " + theDetails.get(new String("User-Agent")));
                   System.out.println("\n---------- " + theDetails.containsKey((String)("User-Agent")));
                   System.out.println("\n---------- " + theDetails.containsKey(new String("Accept")));
                   System.out.println("\n---------- " + theDetails.containsKey((String)("Accept")));
                   System.out.println("\n---------- " + theDetails.containsKey("asdf"));
                   System.out.println("\n---------- " + theDetails.contains("en"));
                   System.out.println("\nEmptry " + theDetails.isEmpty());
                   System.out.println("\nsize " + theDetails.size());
                         System.out.println("\nset " + theDetails.entrySet());
                         System.out.println("\nkeys " + theDetails.keys());

            catch(Exception e)
                  //print the error
            //Close the streams
            catch(Exception e){}
      } //readBrowserDetails()
      public static void main(String args[])
            BrowserDetails anObject;
            anObject = new BrowserDetails();

} //Class HTTPConnection

Here is the output that i get if i test it

---------- null

---------- false

---------- false

---------- false

---------- false

---------- false

Emptry false

size 3

set [Accept-Language = en, User-Agent = HertsWeb/1.0, Accept = application/html]

keys java.util.Hashtable$Enumerator@16f0472

C:\My Documents\Docs\Academic\BSC4\Dissertation\Code\CPD>
Question by:Ziggy100
LVL 92

Accepted Solution

objects earned 240 total points
ID: 8095829
looks like a problem with leading/trailing spaces, try:


Expert Comment

ID: 8099731
Yes, you do indeed have a problem(?) with the whitespace. The key ends ups as "Accept ", not "Accept". ( the values also have a extra leading space ).

More importantly though:
You cannot load a Hashtable with multiple objects of the same key. In your example, "Accept" will ONLY contain "application/html" when you are done.  This is because you are using the same key (Accept) and every put method replaces the previous. KEYS must be unique in Hashtables. "Accept".hashcode() = "Accept".hashcode() everytime. ;)

You could solve this by expressing this in the file with one "Accept" header which can have a value of a comma-delim list ( just like HTTP/1.1 ), or by branching on  if(tempKey.equals( "Accept" ))  and handling them one at a time.  Regardless, you cant put them all in the Hashtable with the exact same key at the same time.

Whichever. Hope this helps.  :-)


Expert Comment

ID: 9058841
This old question needs to be finalized -- accept an answer, split points, or get a refund.  For information on your options, please click here-> http:/help/closing.jsp#1 
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LVL 35

Expert Comment

ID: 9693331
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

- Points to objects

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