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How can I make my server recognize more than 1 user's login info in java?

Now I do realize there are lots of the same question but even after reading the answers I seem not to undertsand. So here is the code and I'll explain the problem.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Objects;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class Server implements Runnable {
String firstName;
String lastName;
String password;
private ArrayList<ConnectionHandler> connections;
private ServerSocket server;
private boolean done;
private ExecutorService pool;
public Server() {
connections = new ArrayList<>();
done = false;
}
#Override
public void run() {
try {
server = new ServerSocket(9999);
pool = Executors.newCachedThreadPool();
while (!done) {
Socket client = server.accept();
ConnectionHandler handler = new ConnectionHandler((client));
connections.add(handler);
pool.execute(handler);
}
} catch (Exception e) {
shutdown();
}
}
public void shutdown() {
try {
done = true;
pool.shutdown();
if (!server.isClosed()) {
server.close();
}
for (ConnectionHandler ch : connections) {
ch.shutdown();
}
} catch (IOException e) {
// ignore
}
}
class ConnectionHandler implements Runnable {
private Socket client;
private BufferedReader in;
private PrintWriter out;
public void broadcast(String message) {
for (ConnectionHandler ch : connections) {
if (ch != null) {
ch.sendMessage(message);
}
}
}
public ConnectionHandler(Socket client) {
this.client = client;
}
#Override
public void run() {
try {
out = new PrintWriter((client.getOutputStream()), true);
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out.println("To register type 1,to sign in type 2");
//TODO:for loop so only answer is 1 or 2
String message = in.readLine();
switch (message) {
case "1":
out.println("In order to register please enter your first and last name then set a password.");
out.println("Enter first name:");
firstName = in.readLine();
out.println("Enter last name:");
lastName = in.readLine();
out.println("Finally please set a password.");
password = in.readLine();
//TODO: add parameters for passcode
out.println("Now please type 2 to login");
message = in.readLine();
if (message.equals("2")) {
//TODO: copy paste from line 104-x
}
case "2":
out.println("Please enter your first name:");
String messageLogInFN= in.readLine();
out.println("Please enter your last name:");
String messageLogInLN = in.readLine();
out.println("Enter your password:");
String messageLogInPass = in.readLine();
boolean adminAccount = (messageLogInFN.equals("admin") && messageLogInLN.equals("admin") && messageLogInPass.equals("admin123cat"));
if (adminAccount) {
//TODO: add admin permissions
}
boolean Authentication = ((messageLogInFN.equals(firstName) && messageLogInLN.equals(lastName) && messageLogInPass.equals(password)));
if (Authentication) {
out.println("Welcome " + firstName + " " + lastName + "!");
System.out.println(firstName + " " + lastName + " has logged in." );
} else
out.println("Your name or password incorrect!");
}
} catch (IOException e) {
shutdown();
}
}
public void sendMessage(String message) {
out.println(message);
}
public void shutdown() {
try {
in.close();
out.close();
if (!client.isClosed()) {
client.close();
}
} catch (IOException e) {
//ignore
}
}
}
public static void main(String[] args) {
Server server = new Server();
server.run();
}
So I am learning java and saw a tutorial on youtube for a chat room, I programed it following the tutorial, and then I wanted to have a chat room with accounts so I got to coding. Now here is the thing even though I am able to have several devices connected to the server when 2 accounts register the server forgets the first one so there can only be 1 account at the same time. What I am trying to do is have an account system where everyone has their own account that they log in with their first name, last name and passwords. But it doesnt seem to work. How can I make it so that the server doesn't forget all accounts except for the last one that registered?
Edit: Here is the client code if it helps.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class Client implements Runnable {
private boolean done;
private Socket client;
private BufferedReader in;
private PrintWriter out;
#Override
public void run() {
try {
client = new Socket("127.0.0.1", 9999);
out = new PrintWriter((client.getOutputStream()), true);
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
InputHandler inHandler = new InputHandler();
Thread t = new Thread(inHandler);
t.start();
String inMessage;
while ((inMessage = in.readLine()) != null) {
System.out.println(inMessage);
}
} catch (IOException e) {
shutdown();
}
}
public void shutdown() {
done = true;
try {
in.close();
out.close();
if(!client.isClosed()) {
client.close();
}
} catch (IOException e) {
//ignore
}
}
class InputHandler implements Runnable {
#Override
public void run() {
try {
BufferedReader inReader = new BufferedReader(new InputStreamReader(System.in));
while (!done) {
String message = inReader.readLine();
if(message.equals("/quit")) {
out.println(message);
inReader.close();
shutdown();
} else {
out.println(message);
}
}
} catch (IOException e) {
shutdown();
}
}
}
public static void main(String[] args) {
Client client = new Client();
client.run();
}
}
Also as I said most of this isnt my code and I followed a yt tutorial.

Java showInputDialog when data not correct

import javax.swing.*;
import java.io.Serializable;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
public class Server implements Serializable{
public static void main(String[] args) {
String test1= JOptionPane.showInputDialog(null,"Port(0-65535):","Port",JOptionPane.QUESTION_MESSAGE);
int portnumber = tryParse(test1);
if (portnumber !=0) {
try {
Registry reg = LocateRegistry.createRegistry(portnumber); //Creates and exports a Registry instance on the local host that accepts requests
RmiImplementation imp = new RmiImplementation("C://ServerStorage");
reg.bind("remoteObject", imp);
System.out.println("Server is ready.");
System.out.println(portnumber);
} catch (Exception e) {
System.out.println("Server failed: " + e);
}
}
}
private static Integer tryParse(String text) {
try {
return Integer.parseInt(text);
} catch (Exception e) {
return 0;
}
}
}
The above code helps me to set up my file server.
when the application is run, the dialog port number is requested.
If I type letters instead of numbers the program stops running, but I want it to continue and show me the dialog again.

Try with a do-while,
int portnumber = 0;
do {
String text= JOptionPane.showInputDialog(null,"Port(0-65535):","Port",JOptionPane.QUESTION_MESSAGE);
portnumber = tryParse(text);
}while(portnumber==0);

Two Way Serial Communication- Cannot access string read from Serial Reader Thread

I declared a twoWaySerialComm object to to configure the port connection. Inside the twoWaySerialComm class I created a thread to read the incoming serial data in a class called 'SerialReader'. How can access the serial data from the main thread 'twoWaySerialComm'?
I had read the incoming serial data into 'hex' string in the 'SerialReader' class inside a while loop. I am able to print the incoming data inside the while loop, But i am unable to access this 'hex' string in the 'twoWaySerialComm' class. Why can't I access the 'hex' string outside the while loop? how can this be done?
import gnu.io.CommPort;
import gnu.io.CommPortIdentifier;
import gnu.io.NoSuchPortException;
import gnu.io.PortInUseException;
import gnu.io.SerialPort;
import gnu.io.UnsupportedCommOperationException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
*
* #author asanka
*/
public class TwoWaySerialComm {
private static TwoWaySerialComm twoWaySerialComm;
String read;
private TwoWaySerialComm() throws NoSuchPortException, PortInUseException, UnsupportedCommOperationException, IOException {
String portName = "/dev/ttyUSB0";
CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier(portName);
if (portIdentifier.isCurrentlyOwned()) {
System.out.println("Error: Port is currently in use");
} else {
CommPort commPort = portIdentifier.open(this.getClass().getName(), 2000);
if (commPort instanceof SerialPort) {
SerialPort serialPort = (SerialPort) commPort;
serialPort.setSerialPortParams(115200, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
InputStream in = serialPort.getInputStream();
OutputStream out = serialPort.getOutputStream();
SerialReader reader;
(new Thread(reader = new SerialReader(in))).start();
read = reader.readHex();
} else {
System.out.println("Error: Only serial ports are handled by this example.");
}
}
}
public static TwoWaySerialComm getTwoWaySerialComm() throws NoSuchPortException, PortInUseException, UnsupportedCommOperationException, IOException {
if (twoWaySerialComm == null) {
twoWaySerialComm = new TwoWaySerialComm();
}
return twoWaySerialComm;
}
public String data() {
return read;
}
/**
*
*/
public static class SerialReader implements Runnable {
String hex;
InputStream in;
public SerialReader(InputStream in) {
this.in = in;
}
public void run() {
byte[] buffer = new byte[1024];
int len;
try {
while ((len = this.in.read(buffer)) > -1) {
hex = new String(buffer, 0, len).replaceAll("\\s", "");
Thread.sleep(1000);
System.out.println(hex);
}
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException ex) {
Logger.getLogger(TwoWaySerialComm.class.getName()).log(Level.SEVERE, null, ex);
}
}
public String readHex() {
return hex;
}
}
/**
*
*/
public static class SerialWriter implements Runnable {
OutputStream out;
public SerialWriter(OutputStream out) {
this.out = out;
}
public void run() {
try {
int c = 0;
while ((c = System.in.read()) > -1) {
this.out.write(c);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

As far as I can see, you're running the read operation in another Thread. When calling the readHex() method, that Thread probably hasn't filled in the hex field yet.
You'll need to call join() on the new Thread first, to ensure it has finished.
Or use the CompletableFuture from the java.util.concurrent package.

Use data from different class in the current project java

I'm facing a problem regarding of using the data from rf transmision on a class that I wish to use to store on the database. Code 1 is the code for the RF transmission. Is there anyway I can use the data in the
highlight of data to be used in code 1?
public synchronized void serialEvent(SerialPortEvent oEvent) {
if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=input.readLine();
String[] parts = inputLine.split(",");
String part1 = parts[0];
String part2 = parts[1];
System.out.print(part1); // data to be used
System.out.print(" , ");
System.out.println(part2); //data to be used
//System.out.println(data);
code 1
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import java.util.Enumeration;
public class test implements SerialPortEventListener {
SerialPort serialPort;
/** The port we're normally going to use. */
private static final String PORT_NAMES[] = {
"COM4", // Windows
};
/**
* A BufferedReader which will be fed by a InputStreamReader
* converting the bytes into characters
* making the displayed results codepage independent
*/
private BufferedReader input;
/** The output stream to the port */
private OutputStream output;
/** Milliseconds to block while waiting for port open */
private static final int TIME_OUT = 2000;
/** Default bits per second for COM port. */
private static final int DATA_RATE = 9600;
public void initialize() {
CommPortIdentifier portId = null;
Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();
//First, Find an instance of serial port as set in PORT_NAMES.
while (portEnum.hasMoreElements()) {
CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
for (String portName : PORT_NAMES) {
if (currPortId.getName().equals(portName)) {
portId = currPortId;
break;
}
}
}
if (portId == null) {
System.out.println("Could not find COM port.");
return;
}
try {
// open serial port, and use class name for the appName.
serialPort = (SerialPort) portId.open(this.getClass().getName(),
TIME_OUT);
// set port parameters
serialPort.setSerialPortParams(DATA_RATE,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
// open the streams
input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
output = serialPort.getOutputStream();
// add event listeners
serialPort.addEventListener(this);
serialPort.notifyOnDataAvailable(true);
} catch (Exception e) {
System.err.println(e.toString());
}
}
/**
* This should be called when you stop using the port.
* This will prevent port locking on platforms like Linux.
*/
public synchronized void close() {
if (serialPort != null) {
serialPort.removeEventListener();
serialPort.close();
}
}
/**
* Handle an event on the serial port. Read the data and print it.
*/
public synchronized void serialEvent(SerialPortEvent oEvent) {
if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
try {
String inputLine=input.readLine();
String[] parts = inputLine.split(",");
String part1 = parts[0];
String part2 = parts[1];
System.out.print(part1); // data to be used
System.out.print(" , ");
System.out.println(part2); //data to be used
//System.out.println(data);
} catch (Exception e) {
System.err.println(e.toString());
}
}
// Ignore all the other eventTypes, but you should consider the other ones.
}
public static void main(String[] args) throws Exception {
test main = new test();
main.initialize();
Thread t=new Thread() {
public void run() {
//the following line will keep this app alive for 1000 seconds,
//waiting for events to occur and responding to them (printing incoming messages to console).
try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
}
};
t.start();
System.out.println("Started");
}

I am probably still confused as to what your asking. I think the simplest way for another class to use the variables would be for it to be passed the values in arguments to one of its functions.
eg.
class ClassThatUsesPart1Part2 {
public void usePart1Part2(String part1, String part2) {
// put code that uses part1 and part2 here
}
}
Add another variable to your class.
private BufferedReader input;
/** The output stream to the port */
private OutputStream output;
/** Milliseconds to block while waiting for port open */
private static final int TIME_OUT = 2000;
/** Default bits per second for COM port. */
private static final int DATA_RATE = 9600;
/** Variable of class that will use part1, part2.*/
private ClassThatUsesPart1Part2 part12User = new ClassThatUsesPart1Part2();
Then use it within your function.
String inputLine=input.readLine();
String[] parts = inputLine.split(",");
String part1 = parts[0];
String part2 = parts[1];
part12User.usePart1Part2(part1,part2);
Is this what you were looking for or have I just completely misunderstood?

Java socket writeObject stucks

I am trying to create some local chat software.
Everything is working fine but just sticks on one point;
when a user clicks on a button my program gets stuck.
I wrote a modified class which behaves for both the server and the client.
Below is my code:
package connections;
import java.awt.event.ActionEvent;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.nio.channels.SocketChannel;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import ui.ChatWindow;
public class Chat{
private SocketChannel socketChannel;
private ConnectionType connectionType;
private ObjectOutputStream out;
private ObjectInputStream in;
private String strClientName;
private ChatWindow chatWindow;
private String strMessage;
public Chat(SocketChannel socketChannel, ConnectionType connectionType) {
this.socketChannel = socketChannel;
this.connectionType = connectionType;
init();
}
private void init() {
new Thread(this::initThread).start();
}
private void initThread() {
try {
out = new ObjectOutputStream(socketChannel.socket().getOutputStream());
in = new ObjectInputStream(socketChannel.socket().getInputStream());
if (connectionType == ConnectionType.SERVER) {
getClientName();
sendMyName();
} else {
sendMyName();
getClientName();
}
chatWindow = new ChatWindow();
chatWindow.btnSend.addActionListener(this::eventBtnSend);
chatWindow.setTitle(strClientName);
chatWindow.setSize(600, 400);
chatWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
if (connectionType == ConnectionType.CLIENT) {
chatWindow.setVisible(true);
chatWindow.requestFocus();
}
System.out.println("here");
beginChat();
System.out.println("thread ends");
} catch (IOException ex) {
Logger.getLogger(Chat.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void getClientName() {
try {
strClientName = (String) in.readObject();
} catch (IOException | ClassNotFoundException ex) {
Logger.getLogger(Status.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void sendMyName() {
try {
out.writeObject(main.Config.myName);
out.flush();
} catch (IOException ex) {
Logger.getLogger(Status.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void beginChat() {
while (true) {
try {
waitForMessage();
} catch (IOException | ClassNotFoundException ex) {
Logger.getLogger(Chat.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
private void waitForMessage() throws IOException, ClassNotFoundException {
System.out.println("waiting for Message : " + connectionType);
strMessage = (String) in.readObject();
System.out.println("Message received");
chatWindow.txtDisplay.append(strClientName + " : " + strMessage + "\n");
if(chatWindow.isVisible() == false){
chatWindow.setVisible(true);
}
}
private void sendMessage(String strMessage) {
try {
out.writeObject(strMessage);
out.flush();
} catch (IOException ex) {
Logger.getLogger(Chat.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void eventBtnSend(ActionEvent ae){
System.out.println("a");
sendMessage(chatWindow.txtMessage.getText());
System.out.println("b");
chatWindow.txtDisplay.append("Me : " + chatWindow.txtMessage.getText() + "\n");
System.out.println("c");
chatWindow.txtMessage.setText("");
}
}
When the server and client connects I can see this output:
here
waiting for Message : SERVER
here
waiting for Message : CLIENT
But when I click on the send button my program becomes stuck.
After clicking the button I can see:
a on console.

The word is 'blocks'. It's blocking I/O. It blocks.
Don't perform blocking operations on the event thread. All the networking code should run on separate threads. That includes readObject() and writeObject(), and flush(), and creating the streams too.