I read the nio tutorial in www.javaworld.com and magazine. I also read the API. I feel that using NIO is very hard because it's not normal procedure to do IO opreation for me. So, I made the MyPing after I read Ping Example. Please examine my code and teach me a lesson. When All ping operation is done, my connect thread is blocked because connect thread is waiting to get monitor, so I used some trick to quit. I doubt whether I made this program correctly. MyPing works correctly but I'm not sure that my program is reliable.

Here's the code

import java.util.*;

import java.net.*;

import java.nio.*;

import java.nio.channels.*;

import java.io.*;



public class MyPing

{

public static void main(String[] args) throws Exception

{

Target t1 = new Target(args[0]);

Target t2 = new Target(args[1]);



Connector connector = new Connector();

connector.start();



connector.add(t1);

connector.add(t2);

connector.join(500);

connector.shutdown();

}

}





class Target {

private InetSocketAddress netAddress;

private boolean isOpen;



public Target(String target_addr) {

netAddress = new InetSocketAddress(target_addr, 80);

}



public InetSocketAddress getNetAddress() {

return netAddress;

}



public void setIsOpen(boolean result) {

isOpen = result;

}



public boolean getIsOpen() {

return isOpen;

}

}



class Connector extends Thread {

private LinkedList targetList;

private Selector trySelect;

private Printer printerForNotification;

private boolean shutdown;



public Connector() throws IOException {

setName("Connector");



targetList = new LinkedList();

trySelect = Selector.open();

printerForNotification = new Printer(trySelect);

printerForNotification.start();

shutdown = false;

}



public void add(Target t) {

synchronized(targetList) {

targetList.add(t);

targetList.notifyAll();

}

}



public void shutdown() {

shutdown = true;

synchronized(targetList) {

targetList.notifyAll();

}

}



public void run() {

while(shutdown == false) {

try {

Target target;

synchronized(targetList) {

if (targetList.size() == 0) {

targetList.wait();

}



if(shutdown) return;



target = (Target) targetList.removeFirst();

}

SocketChannel try_channel = SocketChannel.open();

try_channel.configureBlocking(false);

try_channel.register(trySelect, SelectionKey.OP_CONNECT);

try_channel.connect(target.getNetAddress());

trySelect.wakeup();

}

catch(InterruptedException ie) {}

catch(IOException ioe) {}



}

}

}



class Printer extends Thread

{

private Selector selectForObservation;



public Printer(Selector target_select) {

setName("Printer");

setDaemon(true);

selectForObservation = target_select;

}



public void run() {

while(true) {

try {

selectForObservation.selectNow();

Set readyKeys = selectForObservation.selectedKeys();

if (readyKeys.size() == 0) continue;



for(Iterator i = readyKeys.iterator(); i.hasNext(); ) {

SelectionKey key = (SelectionKey)i.next();

i.remove();



SocketChannel connected_channel = (SocketChannel)key.channel();

System.out.println(connected_channel.socket().toString());

connected_channel.close();

}

}

catch(IOException ioe) {}

catch(ClosedSelectorException cse) {}

}

}

}

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