I need help with building a bidding app

[foggy nymph]

He's in denmark, my dream country

but messaging him require money on linked in sth and it's very expensive for me in the 3rd world

may be i will do very simple app

[foggy nymph]

@forest lion I have decided to submit the minecraft command-like app

@forest lion I have decided to ignore Serialization

[sick thistle]

Hello bro, myself saj. Professional software engineer I helped students in their studies like programming websites mobile apps. So if you want help in your assignment you can tell me

[foggy nymph]

oh i really need help right now in JavaFX . I have decided to study JavaFX on a book of Jenkov, however i face a lots of challenges. Particularly, i want to use borderpane for my app, and the right side of it is supposed to contains a constant self update display of a ConcurrentHashMap. But i really dont know how to do it. Please help.
By the way i am also facing deadline in 31 may, so we have 10 more days.

in my bidding project, i want the right side of it is like : Name of the person, below it is his items
for example it should be like
Anna sells:

• apple
• banana
• orange
  Bob sells:
• cake
• bread
• flour
  Collin sells:
• apartments
• flat

like that

and i want it to self update

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.

[foggy nymph]

https://gist.github.com/Together-Java-Bot/045733de79625abd505b383cc6c99c54

@sick thistle btw this is my current project

https://drive.google.com/file/d/1JC3T56T9IDVr0d6oVyoO9ygocTh5RfOt/view?usp=drive_link

@sick thistle this is video of how it works. please help thx

[forest lion]

this is a place to provide help, not to sell help

just fyi

[foggy nymph]

oh so he sells tutoring service

that can be expensive for me in the 3rd world

[forest lion]

maybe not

[foggy nymph]

here is the file translated to english

by the way i have a problem on my AuctionClient.java file, there is a singleton Passwordmanager that spawn with each client, instead of all clients the same manager, but i dont know how to deal with that. I have tried creating a new socket 9001 between auctionclient.java and chatserver.java, but idk this doesnt work (the server usually shut down)

i mean there must be a fundamental issue in the way i coded it

[forest lion]

? there is a singleton Passwordmanager that spawn with each client, instead of all clients the same manager, but i dont know how to deal with that.

it needs to be on the server

not the client

there are N clients, only 1 server

[foggy nymph]

i mean, i dont know how to make the server send information back to Auction Client

The server never sent any information back to AuctionClient.java file (it was originally named Client.java, but i renamed it to AuctionClient.java bc it was red)

[foggy nymph]

i mean like when i enter password, i need ChatServer.java send information back to AuctionClient.java so that it knows whether to continue or not, but i just dont know how to send it back

🆘

@forest lion I have decided to make another socket to connect auction client.java with ChatServer.java, but it make the server always shut down

of course it is supposed to be on the server 😭

[forest lion]

sendToClient!

[forest lion]

you send info with sendToClient!

[foggy nymph]

but it sends to ChatClient.java, not AuctionChat.java

i meant AuctionClient.java

[forest lion]

i think i see what is happening

so ChatClient.java has an onMessage and you can handle things there

[foggy nymph]

i mean like if i have another case in ChatClient.java, how do i send information from ChatClient.java to AuctionClient.java?

[forest lion]

can you share both files?

[foggy nymph]

https://gist.github.com/Together-Java-Bot/045733de79625abd505b383cc6c99c54

[forest lion]

okay so a few things i'm noticing off the bat

      final int[] id = {0};
      final int[] check = {0};

this actually won't work like you think it will.

good news is that the easy fix is this

      final AtomicInteger id = new AtomicInteger(0);
      final AtomicInteger check = new AtomicInteger(0);

then instead of id[0] and id[0] = ... use id.get() and id.set(...)

      PasswordManagementSystem passwordManagementSystem = PasswordManagementSystem.getInstance();
      GUIIO.println("Please enter your username and password");

      String[] linePass = GUIIO.readln().split("\\s+");
      if (linePass.length < 2) {
        GUIIO.println("Invalid input");
        return;
      }
      String username = linePass[0];
      String password = linePass[1];
      passwordManagementSystem.addUser(username, password);

so here the server needs to be managing users, not the client

the client takes input but then needs to send a message to the server

now to make these communicate:

there are more "correct" options and there is an option we can do only if the only thing that needs to be communicated is that you logged in

and if you only log in once

yeah a lot of stuff you should be doing on the server you are doing in the client

          Thread timer = new Thread(() -> {
            try {
              Thread.sleep(120000);
              GUIIO.println(" The auction ended after 120 secs");
              client.sendToServer(new SeeTheList(true));
              GUIIO.println(" You have 20 secs to view the result");
              Thread.sleep(20000);
              System.exit(0);
            } catch (InterruptedException e) {
              e.printStackTrace();
            }
          });

import java.util.concurrent.LinkedBlockingQueue;

class Example {
    private final LinkedBlockingQueue<String> out;

    Example(LinkedBlockingQueue<String> out) {
        this.out = out;


    }

    void spin() {
        Thread.startVirtualThread(() -> {
            while (true) {
                try {
                    Thread.sleep(1000);
                    out.add("ping");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

public class Queues {

    void main() {

        var q = new LinkedBlockingQueue<String>();
        var example = new Example(q);
        example.spin();

        while (true) {
            var msg = q.poll();
            if (msg != null) {
                IO.println(msg);
            }
        }
    }
}

here is your basic example of how to make things on different threads communicate

step 1: Make sure the two things (in this case ChatClient and AuctionClient) share the exact same LinkedBlockingQueue

step 2: have one thing .add messages to the queue

step 3: have the other thing .poll() the queue (or .take() if you want to wait)

so in this case when AuctionClient sends a message to the server "new Login(username, password)", you want to then wait on a message from ChatServer saying whether those credentials were correct

and obviously you might not want to use Strings

you can also make as many queues as you need

    private record ConnectedClient<ToClient, ClientState>(
            LinkedBlockingDeque<ToClient> outgoing,
            Thread outgoingThread,
            Thread incomingThread,
            AtomicReference<ClientState> state
    ) {
    }

Just for reference, in the server code I wrote this is how I send messages to the clients. We have one part of the system put the messages to send into a queue

    /// Sends a message to a specific connected client
    protected final boolean sendToClient(ClientId id, ToClient message) {
        var client = clients.get(id);
        if (client == null) {
            LOG.warn("No connected client with id: {}", id);
            return false;
        }

        client.outgoing.add(message);
        return true;
    }

Then another part of the system waiting for messages to come in

                    Thread outgoingThread = Thread.startVirtualThread(() -> {
                        while (true) {
                            if (Thread.interrupted()) {
                                break;
                            }
                            try {
                                try {
                                    var message = q.take();
                                    out.writeObject(message);
                                } catch (InterruptedException e) {
                                    LOG.info("Client connection closed. client_id={}", id);
                                    break;
                                }
                            } catch (Exception e) {
                                LOG.error("Error sending client message", e);
                            }
                        }
                    });

[foggy nymph]

so i will use your example and make AuctionClient and ChatSErver.java communicate?

Dont use ChatClient's switch case anymore?

[forest lion]

eh - it depends

i'd say more only specific messages you'd forward out of ChatClient

[foggy nymph]

i think it might be shorter and easier to understand if i can somehow send information from ChatClient.java to AuctionClient.java

[forest lion]

the problem is that ChatClient works "reactively" - when the server gives it a message it responds

[foggy nymph]

okay, so switch case of ChatClient.java is only to forward to terminal

[forest lion]

while AuctionClient works imperatively

so you'd need to be explicitly checking "do i have a new message? if so..."

[foggy nymph]

so AuctionClient works extremely urgently

[forest lion]

which is a little complicated to get right and you might end up making a new thread regardless

[forest lion]

lets say either forward to terminal or forward again to AuctionClient

idk

you (probably?) are at a point where you will pass; though idk

you are definitely learning more now than you were before

[foggy nymph]

I don't think every client have their own pwd manager is a good idea though

[forest lion]

yeah thats pretty bad

you want that on the server

part of what we did here is that we modeled the whole system as "client and server send messages at their leisure"

and thats a little annoying for logging in because...well thats a "client sends a message, waits for server response" kind of thing

its not the worst though

[foggy nymph]

i'm sure i will be able to do that, i will "just write", send problem back and u fix both mindset and the code. easy. I still have 9 more days

[forest lion]

make sure to save your progress as you go

in case you break something

[foggy nymph]

i push it on github everyday

[forest lion]

okay good

[foggy nymph]

The app IntelliJ has Local History feature so no worry

@forest lion It's red, what do i do?

[forest lion]

did you just replace check[0] with check?

#1502554469592993862 message

[foggy nymph]

yes, i replaced check[0] with check, because that's also red

[forest lion]

read what I wrote

#1502554469592993862 message

[foggy nymph]

okay

[foggy nymph]

OKay so i will add 1 more case in ChatServer.java and make Serversleeps

[forest lion]

Maybe do that one after login

That can get tricky as well

[foggy nymph]

so i still create a new thread, but i dont need a new port anymore?
and i will need to be explicitly checking "do i have a new message? if so..."
how do I "explicitly checking "do i have a new message? if so..." "?

[forest lion]

you only need ports when two things are communicating over a network

how do I "explicitly checking "do i have a new message? if so..." "?
I gave you a minimal example above with .poll

[foggy nymph]

1. But AuctionClient can easily send message to ChatServer using client.sendToServer. I only had problem sending stuff the other way around. Do i still use client.sendToServer?
2. what's AtomicReference<ClientState> state ? What is Reference? What is state?
3. so the "part of system waiting for messages to come in" is put in a case of switchcase in ChatServer.java ? If it is "wait to come in", then why it is named "outgoingThread" ?

[forest lion]

for #2 its just a demonstration of how i made the library you are using

that isn't code you should write

#3 has the same answer

i can explain, but its not worth your time right now

[foggy nymph]

apparently, i have a habit of skimming through text due to reading AI's answer (most of its answers are very useless).
yeah and i usually asked AI questions like that.

[forest lion]

you asked an AI about what I just wrote?

[foggy nymph]

no, i mean the way i ask AI sounds stupid like that

[forest lion]

okay

now for #1 i think the word "client" is what is throwing you

[foggy nymph]

its aswer is clearly unreliable now

[forest lion]

AuctionClient isn't really the "client" to the server

its just another part of your program, the one that interacts with the actual client (which is ChatClient)

[foggy nymph]

that's feels off because AuctionClient receives messages from the prompt.

[forest lion]

right but thats not a "client to the server"

thats an "interface for your user"

User -> Interface -> Client (for the server) <-> Server

this is how your program more or less works right now

your user can do things with the interface and that part of the program knows how to send info to the client

and then the client can send info to and from the server

your issue right now is that (other than printlns) it is hard for the client to then communicate to the interface (the part that accepts input, makes a window, etc)

and that is what the LinkedBlockingQueue is for

User -> Interface <-> Client (for the server) <-> Server

filling in that part of the flow

[foggy nymph]

okay i will try to write

[foggy nymph]

@forest lion uhm it's red, i think i did something wrong. Btw the void() method is weird, i cannot easily plug it in.

[foggy nymph]

uhm i actually dont know how to make both of them share the exact LinkedBlockingQueue. may be make AuctionClient extends ChatClient.java?

[forest lion]

no definitely not that

you add an extra argument to the constructor of ChatClient

right now it takes two arguments, add a third

and when I say "I made you an example" zero times out of 100 am I telling you "copy paste this exactly into your code"

I am not making you something to plug in

you need to read, understand, and generalize that knowledge

[foggy nymph]

but if add an extra argument in the port somewhere it will says expected 3 arguments and idk how to get the 3rd

[forest lion]

new ChatClient(<arg1>, <arg2>, <arg3>) when you construct it

then go into ChatClient and add an argument to the constructor

ChatClient(String host, int port, <....>) {

}

[foggy nymph]

in the place in AuctionClient next to port 9009 it demands a linkedqueue for the 3rd parameter

[forest lion]

ok

[foggy nymph]

oh i think i realised something

[foggy nymph]

now both have the same LinkedQueue. i never realised that ChatClient is constructed inside AuctionClient

[forest lion]

okay now you have a way for ChatClient to send Booleans to AuctionClient

[foggy nymph]

@forest lion actually i have not. In AuctionClient i cant do client.spin() and receive the answer

idk what i did wrong

may be im too sleepy. its 1am and i took sleeping pill 2 hours ago

[forest lion]

The spin method was illustrative

it makes zero sense for your program

you would want to handle some message in onMessage by pushing to the queue

[forest lion]

maybe, but at some point you need to stop copy pasting things

that isn't how to make a program

it looks like you would want to add to the queue in case LoginValidation

[foggy nymph]

the word spin sounds fun, so i decided to take it.

like the amongus semicolon

[foggy nymph]

so that means use sendToServer

[forest lion]

for what?

you only use that when sending messages to the server

[foggy nymph]

for sending from password and username from AuctionClient.java to server, just like efore

[foggy nymph]

i added but i feels very weird

@forest lion i think i did something wrong. can u fix?

[forest lion]

get rid of spin

[foggy nymph]

okay i will get rid of spin

what should i do now?

[forest lion]

what do you mean?

[foggy nymph]

is my code correct now?

[forest lion]

if your goal was to forward a login validation to the queue - yes

[foggy nymph]

uhm how do i deal with this

May be i put the rest of the code in the while(true) poll statement

i have decided to pull all stuff in the while true receive statement. i only receive the confirmation once so may be that can work

@forest lion this time the code do run but when i open the 2nd client and type the same username it just do not respond at all anymore

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.

[forest lion]

poll returns null if no message is there yet

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.

[forest lion]

you want .take() if you want to wait for a message

[foggy nymph]

https://gist.github.com/Together-Java-Bot/b0c1b2a42e2dfd7ae50c9776d7046db4

[foggy nymph]

now it says WRONG USERNAMe although i typed correct username. I didnt expect this

oh it's supposed to be if msg == false

i think it works now

now i will develop a system that rejects same username

now i will do "Lean IDE features"

i hope @sick thistle will come back and help me with front end

[foggy nymph]

apparantly it doesnt only need to check whether the password exist or not, but also need to check whether the username exist before

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.

[foggy nymph]

@forest lion Um i need help idk why when i type wrong password it is no longer responsive

so you sell tutoring service. I'm sorry i cant afford it

I'm in a 3rd world country very poor 🙁

[zealous spire]

That's strike two since you've been here. No more even hinting of paid help. If you don't want to engage with free help then questions isn't for you. But you're welcome to engage in chit-chat or geek-speak if there's a technical topic you're interested in.

[foggy nymph]

@forest lion In the past, how did you learn JavaFX?

[foggy nymph]

idk why on IDE learning the breakpoints work very well it just dont work in my code.

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.

[foggy nymph]

oh no

@forest lion
So the system you gave me works absolutely fine when i type correct password when i check

Please enter your username and password
[SYSTEM]: 0 has connected
Please enter your username and password to check
received
CORRECT PASSWORD
This is how to use our service: 
  '/place-bid <id>(Int) <amount>(Int)' in order to bid; 
 use  '/list-item' in order to see the list; 
 use '/create-item  <price>(Int) <name>(String)' if want to create an item 
 '/help' if you want help ```

[lethal tinsel]

Detected code, here are some useful tools:

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.

[foggy nymph]

https://gist.github.com/Together-Java-Bot/1d50f237ac4863deb3c22b02231bfe50

OH MY GOD IT WORKS NOW!

@forest lion IT WORKS IT WORKS IT WORKS!!!

@forest lion turns out there was a GUIIO.println() in PasswordManagementSystem and it's not supposed to be there

YAYY!

YOU knew i'd figure it out.

damn it took me a whole day to figure this out

so that's what being a software engineer taste like

😭

[foggy nymph]

@forest lion there is only 1 more bug: if 2nd client type the username and passport of 1st client, he can still login

Apparantly to fix this bug the Passwordmanagement system not only need username and password but also ClientId

I hope he return from the wood soon

[foggy nymph]

i've fixed it all!

@forest lion the app is very good (except front end) now i believe.

[foggy nymph]

@forest lion apparantly, after the auction ended, people can still place bid. idk how to fix this, because i dont know much about threads

[lethal tinsel]

I uploaded your attachments as Gist. This makes them more accessible, for example to mobile users.