Exception in thread "Thread-0" java.lang because object is not initialized

Question

My whole source code is supposed to be a multi-chat created in Java that uses RSA to keep the messages encrypted until the clients receive their message on their side it gets decrypted.

The problem is that I am getting an error in my Thread block. The reason why I am getting an error is because my RSA object named "secret" is null (keep in mind secret is a public object). Which is weird because I initiated my secret object when the user decides to send the message.

Here is my code when I initiate my RSA object called secret:

`

public void sendMessage(){
    try{
        bufferedWriter.write(username); //whatever we send here the client handle
        bufferedWriter.newLine();
        bufferedWriter.flush();

        Scanner scanner = new Scanner(System.in);


        while(socket.isConnected()){
            String messageToSend = scanner.nextLine(); // this reads the user text
            //insert RSA here and huffman
            this.secert = new RSA(messageToSend); //this encrypts the message

            //bufferedWriter.write(username + ": " + messageToSend);
            bufferedWriter.write(username + ": " + secert.getEncrpytMessageString());
            bufferedWriter.newLine();
            bufferedWriter.flush();

        }
    }catch(IOException e){
        closeEverything(socket, bufferedReader, bufferedWriter);
    }
}

`

Here is my code when I decrypt the RSA code which gives me the error. I wrote a comment so it is easy to spot.

`

public void listenForMessage(){

    new Thread(new Runnable() {
        @Override
        public void run() {
            String msgFromGroupChat;
            try{
                while(socket.isConnected()){

                    //msgFromGroupChat = bufferedReader.readLine();
                    msgFromGroupChat = secert.decrypt(bufferedReader.readLine()); //reads broadcast message ERROR HERE

                    //once it reaches the client it should decrypt
                    //msgFromGroupChat = secert.decrypt(msgFromGroupChat);

                    System.out.println(msgFromGroupChat);
                }
            }
             catch(IOException e){
                closeEverything(socket,bufferedReader,bufferedWriter);
            }
        }
    }).start();
}

`

This is the error message I received:

Exception in thread "Thread-0" java.lang.NullPointerException
  at Client$1.run(Client.java:78)
  at java.base/java.lang.Thread.run(Thread.java:834)

I expected that my message would be decrypted and it would be able to print out into the console of the other user that is in this local server.

One thing I is tried initializing my RSA object named secret out of the while(socket.isConnected()) block in the sendMessage method. This did not help because I ended up getting the same error message. So, I think there is an issue in the thread block in the method called listenForMessage.