来自孙卫琴的Java网络编程，第四章，这段代码感觉有问题啊,第45行的 synchronized(gate){}

这句代码怎么理解啊，可以这样写吗？

1.[文件] EchoServer.java ~ 4KB     下载(19)

package thread2;

import java.io.*;

import java.nio.*;

import java.nio.channels.*;

import java.nio.charset.*;

import java.net.*;

import java.util.*;

public class EchoServer{

private Selector selector = null;

private ServerSocketChannel serverSocketChannel = null;

private int port = 8000;

private Charset charset=Charset.forName("GBK");

public EchoServer()throws IOException{

selector = Selector.open();

serverSocketChannel= ServerSocketChannel.open();

serverSocketChannel.socket().setReuseAddress(true);

serverSocketChannel.socket().bind(new InetSocketAddress(port));

System.out.println("服务器启动");

}

public void accept(){

for(;;){

try{

SocketChannel socketChannel = serverSocketChannel.accept();

System.out.println("接收到客户连接，来自:" +

socketChannel.socket().getInetAddress() +

":" + socketChannel.socket().getPort());

socketChannel.configureBlocking(false);

ByteBuffer buffer = ByteBuffer.allocate(1024);

synchronized(gate){

selector.wakeup();

socketChannel.register(selector,

SelectionKey.OP_READ |

SelectionKey.OP_WRITE, buffer);

}

}catch(IOException e){e.printStackTrace();}

}

}

private Object gate=new Object();

public void service() throws IOException{

for(;;){

synchronized(gate){}

int n = selector.select();

if(n==0)continue;

Set readyKeys = selector.selectedKeys();

Iterator it = readyKeys.iterator();

while (it.hasNext()){

SelectionKey key=null;

try{

key = (SelectionKey) it.next();

it.remove();

if (key.isReadable()) {

receive(key);

}

if (key.isWritable()) {

send(key);

}

}catch(IOException e){

e.printStackTrace();

try{

if(key!=null){

key.cancel();

key.channel().close();

}

}catch(Exception ex){e.printStackTrace();}

}

}//#while

}//#while

}

public void send(SelectionKey key)throws IOException{

ByteBuffer buffer=(ByteBuffer)key.attachment();

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

buffer.flip(); //把极限设为位置

String data=decode(buffer);

if(data.indexOf("\n")==-1)return;

String outputData=data.substring(0,data.indexOf("\n")+1);

System.out.print(outputData);

ByteBuffer outputBuffer=encode("echo:"+outputData);

while(outputBuffer.hasRemaining())

socketChannel.write(outputBuffer);

ByteBuffer temp=encode(outputData);

buffer.position(temp.limit());

buffer.compact();

if(outputData.equals("bye\r\n")){

key.cancel();

socketChannel.close();

System.out.println("关闭与客户的连接");

}

}

public void receive(SelectionKey key)throws IOException{

ByteBuffer buffer=(ByteBuffer)key.attachment();

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

ByteBuffer readBuff= ByteBuffer.allocate(32);

socketChannel.read(readBuff);

readBuff.flip();

buffer.limit(buffer.capacity());

buffer.put(readBuff);

}

public String decode(ByteBuffer buffer){ //解码

CharBuffer charBuffer= charset.decode(buffer);

return charBuffer.toString();

}

public ByteBuffer encode(String str){ //编码

return charset.encode(str);

}

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

final EchoServer server = new EchoServer();

Thread accept=new Thread(){

public void run(){

server.accept();

}

};

accept.start();

server.service();

}

}

/****************************************************

* 作者：孙卫琴 *

* 来源：<> *

* 技术支持网址：www.javathinker.org *

***************************************************/