Help needed shuffling with pre-planted number

[rich ore]

Making card game with clients and a server. Only form of communication between them are strings. To shuffle the deck and have it be the same amongst all clients, I have determined that the server needs to make a random number, than pass this number to all the clients. The clients, using the same number the other clients are using, will shuffle the ArrayList that holds the deck of card objects. This way, all clients will have the same exact deck afterwards. How would I go about making a randomizer that uses a single number to control the randomization? Thanks for your time (and possibly) your help!

[blissful jetty]

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[spark barn]

why not just shuffle the deck on the server and send that data?

much less data duplication and you maintain the server as the source of truth

[rich ore]

As I said, I can only send string values between them. This is an ArrayList object that holds many Card objects

[spark barn]

...i don't see how that's an issue

to continue my previous thought; wait, is this a card game as in playing cards

[rich ore]

How do I send an ArrayList as a string and than from a string to an object?

[rich ore]

Yes

[spark barn]

serialization/encoding

[spark barn]

i was initially understanding it as like a tcg kind of card game, where the server would also have to send what cards were in the deck to begin with, this makes more sense mb

[rich ore]

The Arraylist holds roughly 50 cards. It would be a rather beefy string- are you sure no data would get lost on the way?

[rich ore]

All good

[spark barn]

you could do it within 100 chars = 800 bits

that's not really beefy

[rich ore]

Each card holds it's image in string value and card type in string value

[spark barn]

you don't need to send the entire card, every ace of spades is equal, you only need to send the value and suit of the card

[rich ore]

Actually I'm making uno lol

[spark barn]

oh that wouldn't be playing cards then

[rich ore]

for instance, the red 5 card's string value is "r 5"

[spark barn]

also uno uses a deck of 100+ cards, btw

[rich ore]

I'm aware

[spark barn]

iirc it's 110

[rich ore]

Simplifying it for myself lmao

So you're saying my best solution would just to use Collections.shuffle and than pass this as a string, than back into an object again?

[spark barn]

yeah
the space there isn't really necessary, and if you design an encoding that always uses 2 chars per card, you could achieve the 816 bits i mentioned

[spark barn]

not the best solution anymore considering the cards are known

[rich ore]

i'm using parse(" ") to separate the many messages i'm sending so for the way i have it set up it is

(i work with what i have stored in my brain)

[spark barn]

i was assuming you had sent the deck and then a rng number to shuffle afterwards (as opposed to sending the shuffled deck to begin with), because i had the tcg kind of card game in mind

[rich ore]

ah no

each client holds their own deck

[spark barn]

so yeah your idea works fine here

[rich ore]

Ah ok

[spark barn]

well i mean not quite

it's the same as the servers (or well they should be), except they're generated instead of received

[rich ore]

Yes quite, each client holds their own deck and send messages to the server telling each other client what each client is doing. If a client draws a card, that client gets the card but all the other clients get rid of the top card in the deck

[spark barn]

still maintains the important thing, which is the server being the source of truth, so i see no issue with your solution

[rich ore]

I may not be doing it in the best way but It's what i have written

[rich ore]

Alright. So how would I do it lol

[spark barn]

Collections.shuffle has an overload that lets you provide a Random, a source of randomness
https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#shuffle-java.util.List-java.util.Random-
Random can be seeded
https://docs.oracle.com/javase/8/docs/api/java/util/Random.html#Random-long-

[rich ore]

So by "random can be seeded", you mean I can have the same "random" number across all clients?

Because the issue is figuring out how to randomize with just one number

I can easily have the server just make up a number and pass it to the clients

[spark barn]

yep

[spark barn]

yeah that's how seeds work

[rich ore]

OOH

So you're saying it'll be just like Collections.shuffle(insert here)

but the same across all clients

or have I completely missed the point?

[spark barn]

i mean yeah that's how you shuffle a list

the point is that you can get consistent shuffling though
Collections.shuffle(deck, new Random(seed));

[rich ore]

with "seed" being just a number (EX: 23737)?

(I read the docs, just a sanity check for me from mr pro himself)

Just checked, you are completely right

Thank you very much, I joined this server just for this- is there a way to give you points for helping me or something?

[blissful jetty]

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[spark barn]

/run

import java.util.*;
import java.util.stream.*;
Random r1 = new Random(1);
Random r2 = new Random(1);
List<Integer> l1 = new ArrayList<>(List.of(0, 1, 2, 3, 4));
List<String> l2 = new ArrayList<>(List.of("a", "b", "c", "d", "e"));
System.out.println(IntStream.range(0, 5).mapToObj((i) -> String.valueOf(r1.nextInt())).collect(Collectors.joining(" ")));
System.out.println(IntStream.range(0, 5).mapToObj((i) -> String.valueOf(r2.nextInt())).collect(Collectors.joining(" ")));
Collections.shuffle(l1, r1);
Collections.shuffle(l2, r2);
System.out.println(l1);
System.out.println(l2);

[inner scroll]

Here is your java(15.0.2) output @spark barn

-1155869325 431529176 1761283695 1749940626 892128508
-1155869325 431529176 1761283695 1749940626 892128508
[0, 2, 3, 1, 4]
[a, c, d, b, e]

[rich ore]

ggwp

[spark barn]

mobile dev moment

fml

[rich ore]

Just gonna close this if there's no way to reward you

[spark barn]

sec

[rich ore]

(i tried it out and it is working perfectly)

[spark barn]

there we go

[spark barn]

it'll come up when closing the post

[rich ore]

Ah, alrighty

Thank you very much!

[blissful jetty]

If you are finished with your post, please close it.
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