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POwhy it returns null pointer exception (server side )
 

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  1. POwhy it returns null pointer exception (server side )
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    <p>this is my server class which let the clients to chat with each other but it will return nullpointer exception for this line: <code>while (!(line = in.readLine()).equalsIgnoreCase("/quit"))</code> would you please help me?thanks.</p> <p>my ChatHandler class:</p> <pre><code> final static Vector handlers = new Vector(10); private Socket socket; private BufferedReader in; private PrintWriter out; public ChatHandler(Socket socket) throws IOException { this.socket = socket; in = new BufferedReader( new InputStreamReader(socket.getInputStream())); out = new PrintWriter( new OutputStreamWriter(socket.getOutputStream())); } @Override public void run() { String line; synchronized (handlers) { handlers.addElement(this); // add() not found in Vector class } try { while (!(line = in.readLine()).equalsIgnoreCase("/quit")) { for (int i = 0; i &lt; handlers.size(); i++) { synchronized (handlers) { ChatHandler handler = (ChatHandler) handlers.elementAt(i); handler.out.println(line + "\r"); handler.out.flush(); } } } } catch (IOException ioe) { ioe.printStackTrace(); } finally { try { in.close(); out.close(); socket.close(); } catch (IOException e) { e.printStackTrace(); } finally { synchronized (handlers) { handlers.removeElement(this); } } } } </code></pre> <p>a part of client class:</p> <pre><code> String teXt = MainClient.getText(); os.println(teXt); os.flush(); try { String line = is.readLine(); setFromServertext("Text recieved:"+line+"\n"); is.close(); is.close(); c.close(); } catch (IOException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } </code></pre>
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    1. COYou've posted a handful questions about `NullPointerException` before and you were told how to ask it the smart way in the future and you were also explained to a fairly high degree how to debug and naildown the root cause. Have you learnt from it at any way? Do you for instance *see* that `in.readLine()` may for instance return `null` so that `.equalsIgnoreCase()` ain't going to work at all?
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