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I have a hash table and I want to send it through by Datagram Socket. So to do this I need to have a byte array. How can I convert my hash table to a byte array? I've ignore filling a hash table I've tried do this by this way:

    Hashtable<String, String> valueNick = new Hashtable<>();
    nickStr = valueNick.toString();
    byte[] bufferNick = nickStr.getBytes();
    for (int i = 0; i < bufferNick.length; i++) {
             System.out.print(bufferNick[i] + " ");
        }

But nothing has been printed. Thanks very much for any help or advise.

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6
  • possible duplicate of What is object serialization? Commented Aug 3, 2015 at 7:19
  • Have you added any thing in the Hashtable? Commented Aug 3, 2015 at 7:20
  • @Ankushsoni Yes, I just ignored it. Commented Aug 3, 2015 at 7:22
  • @dotvav Maybe but I don't want to save it into a file. Commented Aug 3, 2015 at 7:24
  • @James: which Jdk version are you using? Commented Aug 3, 2015 at 7:30

2 Answers 2

Reset to default
2

Consider checking out ObjectOutputStream and ObjectInputStream for this purpose

Check out this tutorial for an example and explanation

The following is an example to serialize the table:

ByteArrayOutputStream byteStream = new ByteArrayOutputStream(5000);
ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(byteStream));

// writes the object into a bytestream
oos.writeObject(valueNick);
oos.close();

byte[] sendBuf = byteStream.toByteArray();
// now send the sendBuf via a Datagram Socket

The following is an example to read the object:

ByteArrayInputStream byteStream = new ByteArrayInputStream(recvBuf);
ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(byteStream));
Hashtable<String, String> msg = (Hashtable<String, String>) ois.readObject();
ois.close();
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1 Comment

plus1 Since this may be the right way to go, consider to extend the answer a little more with an example. Thanks
1

I have modified the code(added value in it)

Hashtable<String, String> valueNick = new Hashtable<>();    
    valueNick.put("name", "Ankush");
    valueNick.put("lastName", "Soni");
        String nickStr = valueNick.toString();
        byte[] bufferNick = nickStr.getBytes();
        for (int i = 0; i < bufferNick.length; i++) {
                 System.out.print(bufferNick[i] + " ");
            }   }

It is printing below output:

123 108 97 115 116 78 97 109 101 61 83 111 110 105 44 32 110 97 109 101 61 65 110 107 117 115 104 125

Edit: With the empty Hashtable also I am able to print the byte data which is

123 125

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1 Comment

My hash table has value, I just ignored it.

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