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Project java NullPointerException when trying to read a csv file

I have a csv file that my class with the code below is trying to read that data to use in my project, but when i run the project, I have a NullPointerException like the csv file is null, but he isn't. The path of the csv file is right and apparently I don't have any error in my class too, what I am missing?
package main.java.br.com.quantumfinance.selecaoEstagio.leitor;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
public class LeitorDeArquivo {
public List<String> lerArquivo() {
try (InputStream resourceAsStream = LeitorDeArquivo.class.getResourceAsStream("/acoes.csv")) {
// Leitura do arquivo.
BufferedReader br = new BufferedReader(new InputStreamReader(resourceAsStream));
// ignora a primeira linha
br.readLine();
List<String> cotacoes = new ArrayList<>();
String linha;
while ((linha = br.readLine()) != null) {
cotacoes.add(linha);
}
return cotacoes;
} catch (FileNotFoundException e) {
System.out.println("Arquivo n�o encontrado.");
e.printStackTrace();
} catch (IOException e) {
System.out.println("Erro de IO.");
e.printStackTrace();
}
throw new RuntimeException("Erro na leitura do arquivo, consulte o console para maiores detalhes.");
}
}
This is the error that I receive when trying to run the project
Exception in thread "main" java.lang.NullPointerException
at java.base/java.io.Reader.<init>(Reader.java:168)
at java.base/java.io.InputStreamReader.<init>(InputStreamReader.java:76)
at main.java.br.com.quantumfinance.selecaoEstagio.leitor.LeitorDeArquivo.lerArquivo(LeitorDeArquivo.java:17)
at main.java.Questoes.main(Questoes.java:26)
This is the project structure

Writing a file to java without erasing what's previously written in said file

I want to write a program that keeps what I've written in my file previously, and continually adds to it, instead of erasing it all every time I run the program.
import java.util.Scanner;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.lang.Math;
class Movie_Ratings_2 {
public static void main(String[] args) {
Scanner n = new Scanner (System.in);
String fileName = "output.txt";
String x = n.nextLine();
try {
PrintWriter outputStream = new PrintWriter(fileName);
outputStream.println(x);
outputStream.close();
outputStream.flush();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

No Action works after Enabling ServerSocket in JAVA

I have created a Server Socket and enabled it to listen to incoming streams.But after enabling the connection it should display a dialog Box showing message "Server Started" ,but it does not appear . I have noticed that after enabling the socket no code after that works. I have tried searching a lot about this but seem to find no suitable answer.Here is my code:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.net.*;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
public class Server
{
public Server(int i1) throws Exception{
ServerSocket MySock=new ServerSocket(i1);//opening server socket
Socket Sock=MySock.accept();//listening to client enabled
JOptionPane.showMessageDialog(null, "Server Started");
}
public static void main(String[] args) {
try {
new Server(2005);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

The problem is that ServerSocket.accept() is blocks until a connection is made..
So the JOptionPane.showMessageDialog(...) will not be executed until someone is connecting to the serversocket.
Here is a solution that handles the ServerSocket in a separate thread
import java.io.IOException;
import java.net.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import javax.swing.*;
public class Server
{
public Server(int i1) throws Exception{
Runnable serverTask = () -> {
try {
ServerSocket MySock=new ServerSocket(i1);//opening server socket
while (true) {
Socket Sock=MySock.accept();//listening to client enabled
System.out.println("Accept from " + Sock.getInetAddress());
}
} catch (IOException e) {
System.err.println("Accept failed.");
}
};
ExecutorService executorService = Executors.newSingleThreadExecutor();
executorService.submit(serverTask);
JOptionPane.showMessageDialog(null, "Server Started");
}
public static void main(String[] args) {
try {
new Server(2005);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

Server(Python) - Client(Java) communication using sockets

I try to send a message from server to a client, after client receives the message, it sends back a message to the server and so on. The problem is with receiving the message in python. The loop it's stuck there.
import socket
HOST = "localhost"
PORT = 9999
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('Socket created')
try:
s.bind((HOST, PORT))
except socket.error as err:
print('Bind failed. Error Code : ' .format(err))
s.listen(10)
print("Socket Listening")
conn, addr = s.accept()
while(True):
conn.send(bytes("Message"+"\r\n",'UTF-8'))
print("Message sent")
data = conn.recv(1024)
print(data.decode(encoding='UTF-8'))
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class Main {
static Thread sent;
static Thread receive;
static Socket socket;
public static void main(String args[]){
try {
socket = new Socket("localhost",9999);
} catch (UnknownHostException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
sent = new Thread(new Runnable() {
#Override
public void run() {
try {
BufferedReader stdIn =new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
while(true){
System.out.println("Trying to read...");
String in = stdIn.readLine();
System.out.println(in);
out.print("Try"+"\r\n");
System.out.println("Message sent");
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
sent.start();
try {
sent.join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

The Python code is fine. The problem is that calling out.print in the Java code does not necessarily cause your message to be sent through the socket immediately. Add
out.flush();
immediately after
out.print("Try"+"\r\n");
to force the message to be sent through the socket. (flush "flushes" through the stream any data that has not yet been sent.) The Python should then be able to receive it correctly.

accessing a local file (Java URL)

I'm trying to open a stream to a file on my PC and I'm trying to do it via URL (I know,It's just for leraning purposes)
this is what I'm doing:
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.SocketTimeoutException;
import java.net.URL;
import java.net.URLConnection;
public class URLTyper {
public static void main(String[] args) {
InputStream in=null;
try {
URL url=new URL("file://127.0.0.1/c:/haxlogs.txt");
// in=url.openStream();
URLConnection conn=url.openConnection();
conn.connect();
in=conn.getInputStream();
while (true) {
int read=in.read();
if (read==-1) break;
System.out.write(read);
}
}
catch (SocketTimeoutException e){
System.out.println("timed out");
}
catch (MalformedURLException e) {
System.out.println("URL not valid");
}
catch (IOException e) {
System.out.println("unable to get data");
}
}
}
It exits throwing an IOException ("unable to access data").. why is it not working? shouldn't it get to the file like an ordinary InputStream?
thanks