Reuse a list of Integers

Hello,
I have a (potentially) infinite list of Integers, one for each person current connected to my socket server. These numbers a short, starting at 0,1,2...etc

The idea are these a temporary unique IDs that stay with a user for their duration on my server:
When a user joins they are assigned the first available number.
When a user leaves, their number is recycled and waits for assignment to someone else.

My code allows for these numbers to be as long as I like but I want to keep them short to conserve the number of bytes sent to each client from my server.

I need to reuse these numbers somehow. I have a list of clients in each room but no centralised list, even if I did I would need to run through every client that was on the server (could be many!) so I need a better way of finding the first available number.

I had an idea of using something like:

Code:

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boolean ids[]= = new boolean[100000];

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But it has problem in that it limits me to 100000 clients at any one time! I may have more but I certainly will have fewer in this case the array wastes memory.

I'm just posting here because I'm sure this has already been solved but I had trouble finding any answers with google. Thanks for reading,
Dan

How about using an ArrayList<Integer>?

well if they're just IDs, I would just create a random number. If it clahes with anything, make another random number. Or if it's possible, get the first 6 digits or something of the current tick and use that as an ID.

EDIT: Well I don't know if ticks is supported or not so I would just use get System.nanoTime() or System.currentTimeMillies().

Thanks imorio, Ok I did a quick read up:
- At the moment I am using LinkedLists for my clients in rooms, this is good as I do a lot of iteration and removing from anywhere in the list (when a client leaves)
- ArrayLists are faster in getting the data, but slower in removing elements from anywhere in the list.

I will use an ArrayList as I will only be removing the last element(s) at any one time. Ill get back to you with the results (hopefully!).
Thanks :)

Quote:

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Originally Posted by Dan0100

Thanks imorio, Ok I did a quick read up:
- At the moment I am using LinkedLists for my clients in rooms, this is good as I do a lot of iteration and removing from anywhere in the list (when a client leaves)
- ArrayLists are faster in getting the data, but slower in removing elements from anywhere in the list.

I will use an ArrayList as I will only be removing the last element(s) at any one time. Ill get back to you with the results (hopefully!).
Thanks :)

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BitSets are cheaper than that (one bit per number).

kind regards,

Jos

JosAH - BitSets.

My code if you are interested:

Code:

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private BitSet uuid = new BitSet(10000);
//
//client join method:
int i = uuid.nextClearBit(0);
uuid.set(i, true);
//i is now used as client's ID
//
//client leave method:
uuid.set(client.getID(), false);

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Simple, perfect. Thank you JosAH.

Also yes limited to 10000, but thats 10000 bits now objects floating around ;) I can stretch to 1million hehe.

Quote:

---

Originally Posted by Dan0100

JosAH - BitSets.

My code if you are interested:

Code:

---

private BitSet uuid = new BitSet(10000);
//
//client join method:
int i = uuid.nextClearBit(0);
uuid.set(i, true);
//i is now used as client's ID
//
//client leave method:
uuid.set(client.getID(), false);

---

Simple, perfect. Thank you JosAH.

Also yes limited to 10000, but thats 10000 bits now objects floating around ;) I can stretch to 1million hehe.

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Yup, that's the way to do it; 1 million users is just 256KB of storage (plus a few bytes for the BitSet object itself).

kind regards,

Jos