ConcurrentModificationException e os fail-fast iterators um outro ponto de vista

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.Iterator;
import java.net.*;

public class NonblockingSingleFileHTTPServer {

  private ByteBuffer contentBuffer;
  private int port = 80;

  public NonblockingSingleFileHTTPServer(
   ByteBuffer data, String encoding, String MIMEType, int port)
   throws UnsupportedEncodingException {

    this.port = port;
    String header = "HTTP/1.0 200 OK\r\n"
     + "Server: OneFile 2.0\r\n"
     + "Content-length: " + data.limit() + "\r\n"
     + "Content-type: " + MIMEType + "\r\n\r\n";
    byte[] headerData = header.getBytes("ASCII");

    ByteBuffer buffer = ByteBuffer.allocate(
     data.limit() + headerData.length);
    buffer.put(headerData);
    buffer.put(data);
    buffer.flip();
    this.contentBuffer = buffer;

  }

  public void run() throws IOException {

    ServerSocketChannel serverChannel = ServerSocketChannel.open();
    ServerSocket  serverSocket = serverChannel.socket();
    Selector selector = Selector.open();
    InetSocketAddress localPort = new InetSocketAddress(port);
    serverSocket.bind(localPort);
    serverChannel.configureBlocking(false);
    serverChannel.register(selector, SelectionKey.OP_ACCEPT);

    while (true) {

      selector.select();
      Iterator keys = selector.selectedKeys().iterator();
      while (keys.hasNext()) {
        SelectionKey key = (SelectionKey) keys.next();
        keys.remove();
        try {
          if (key.isAcceptable()) {
            ServerSocketChannel server = (ServerSocketChannel) key.channel();
            SocketChannel channel = server.accept();
            channel.configureBlocking(false);
            SelectionKey newKey = channel.register(selector, SelectionKey.OP_READ);
          }
          else if (key.isWritable()) {
            SocketChannel channel = (SocketChannel) key.channel();
            ByteBuffer buffer = (ByteBuffer) key.attachment();
            if (buffer.hasRemaining()) {
               channel.write(buffer);
            }
            else {  // we're done
               channel.close();
            }
          }
          else if (key.isReadable()) {
            // Don't bother trying to parse the HTTP header.
            // Just read something.
            SocketChannel channel = (SocketChannel) key.channel();
            ByteBuffer buffer = ByteBuffer.allocate(4096);
            channel.read(buffer);
            // switch channel to write-only mode
            key.interestOps(SelectionKey.OP_WRITE);
            key.attach(contentBuffer.duplicate());
          }
        }
        catch (IOException ex) {
          key.cancel();
          try {
            key.channel().close();
          }
          catch (IOException cex) {}
        }
      }
    }
  }

  public static void main(String[] args) {

    if (args.length == 0) {
      System.out.println(
        "Usage: java NonblockingSingleFileHTTPServer file port encoding");
      return;
    }

    try {
      String contentType = "text/plain";
      if (args[0].endsWith(".html") || args[0].endsWith(".htm")) {
        contentType = "text/html";
      }

      FileInputStream fin = new FileInputStream(args[0]);
      FileChannel in = fin.getChannel();
      ByteBuffer input = in.map(FileChannel.MapMode.READ_ONLY, 0, in.size());

      // set the port to listen on
      int port;
      try {
        port = Integer.parseInt(args[1]);
        if (port < 1 || port > 65535) port = 80;
      }
      catch (Exception ex) {
        port = 80;
      }

      String encoding = "ASCII";
      if (args.length > 2) encoding = args[2];

      NonblockingSingleFileHTTPServer server
       = new NonblockingSingleFileHTTPServer(
         input, encoding, contentType, port);
      server.run();

    }
    catch (Exception ex) {
      ex.printStackTrace();
      System.err.println(ex);
    }

  }

}

   /**
   *   Java Network Programming, Third Edition
   *   By Elliotte Rusty Harold
   *   Third Edition October 2004
   *   ISBN: 0-596-00721-3
   */