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POUnexpected multithreaded result and timing
 

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  1. POUnexpected multithreaded result and timing
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    <p>I wrote a simple server. When do I run this server and then immediately open 3 tabs in browser with uri localhost:7777 I expect thread by request, in my case it is 3<br> simultaneously threads (every thread starts at same time and die at about the same time). </p> <p>But I see in console output that first thread started at 0(local minutes):11(local seconds) then second thread started at 0:11 but stopped(why? it's not independent thread?) at reading loop block and resumed execution only after awaking(0:16) of first thread and third thread runs only when the second thread dies(0:21). </p> <p>I expecting following timing:</p> <pre> Connected with Thread-1 0:11 Connected with Thread-2 0:11 Connected with Thread-3 0:11 Disconnect with Thread-1 0:16 Disconnect with Thread-2 0:16 Disconnect with Thread-3 0:16 </pre> <p>What I missed? Why second thread waits awaking of first thread and third thread starts only after death of second thread?</p> <pre><code>public class Starter { public static void main(String args[]){ int port = 7777; try { final ServerSocket socket = new ServerSocket(port); new Thread(new ThreadPool(socket)).start(); } catch (IOException e) { e.printStackTrace(); } } } public class ThreadPool implements Runnable{ protected ServerSocket socket; public ThreadPool(ServerSocket socket){ this.socket = socket; } @Override public void run() { final ExecutorService executors = Executors.newCachedThreadPool(); while(true){ try { final Socket acceptedSocket = this.socket.accept(); //executors.execute(new ThreadWork(acceptedSocket)); new Thread(new ThreadWork(acceptedSocket)).start(); } catch (IOException e) { e.printStackTrace(); } } } } public class ThreadWork implements Runnable { protected final Socket clientSocket; public ThreadWork(Socket clientSocket){ this.clientSocket = clientSocket; } @Override public void run() { try { System.out.println("Connected with " + java.lang.Thread.currentThread().getName() + " " + ((System.currentTimeMillis() / 1000*60) % 60) + ":" + ((System.currentTimeMillis() / 1000) % 60)); System.out.println(" " + clientSocket.toString()); InputStream sin = clientSocket.getInputStream(); OutputStream sout = clientSocket.getOutputStream(); BufferedReader in = new BufferedReader(new InputStreamReader(sin)); OutputStreamWriter out = new OutputStreamWriter(sout); String line = "HTTP/1.1 200 OK\n" + "Date: Thu, 19 Feb 2009 12:27:04 GMT\n" + "Server: Apache/2.2.3\n" + "Last-Modified: Wed, 18 Jun 2003 16:05:58 GMT\n" + "Content-Type: text/html\n" + "Content-Length: 115\n" + "Accept-Ranges: bytes\n" + "Connection: close\n" + "\r\n" + "&lt;html&gt;&lt;head&gt;&lt;title&gt;Hello&lt;/title&gt;&lt;/head&gt;&lt;body&gt;It Works!&lt;/body&gt;&lt;/html&gt;\n"; String requestLine; System.out.println(" Before reading " + java.lang.Thread.currentThread().getName() + " " + ((System.currentTimeMillis() / 1000*60) % 60) + ":" + ((System.currentTimeMillis() / 1000) % 60)); while((requestLine = in.readLine()) != null) { if(requestLine.isEmpty()){ break; } } System.out.println(" Asleep " + java.lang.Thread.currentThread().getName()); java.lang.Thread.sleep(5000); System.out.println(" Awake " + java.lang.Thread.currentThread().getName()); out.write(line); out.flush(); } catch (InterruptedException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { try { clientSocket.close(); } catch (IOException e) { e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates. } System.out.println("Disconnect with " + java.lang.Thread.currentThread().getName() + " " + ((System.currentTimeMillis() / 1000*60) % 60) + ":" + ((System.currentTimeMillis() / 1000) % 60)); } } } </code></pre> <p>Program output</p> <pre> Connected with Thread-1 0:11 Socket[addr=/0:0:0:0:0:0:0:1,port=45416,localport=7777] Before reading Thread-1 0:11 Asleep Thread-1 Connected with Thread-2 0:11 Socket[addr=/0:0:0:0:0:0:0:1,port=45419,localport=7777] Before reading Thread-2 0:11 Awake Thread-1 Disconnect with Thread-1 0:16 Asleep Thread-2 Awake Thread-2 Disconnect with Thread-2 0:21 Connected with Thread-3 0:21 Socket[addr=/0:0:0:0:0:0:0:1,port=45424,localport=7777] Before reading Thread-3 0:21 Asleep Thread-3 Awake Thread-3 Disconnect with Thread-3 0:26 </pre>
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    1. USGerman Malinovsky
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