1、IO的例子/*字节IO*/publicvoidbyteIO()throwsFileNotFoundException, IOException {
FileInputStream fin=newFileInputStream(newFile("D:\\test\\byteio_in.txt"));
FileOutputStream fout=newFileOutputStream(newFile("D:\\test\\byteio_out.txt"));intc = -1;while((c = fin.read()) != -1) {
fout.write(c);
}
fin.close();
fout.close();
}/*字符IO*/publicvoidcharIO()throwsFileNotFoundException, IOException {
FileReader reader=newFileReader(newFile("D:\\test\\chario_in.txt",""));
FileWriter writer=newFileWriter(newFile("D:\\test\\chario_out.txt"));char[] charArr =newchar[512];while(reader.read(charArr) != -1) {
writer.write(charArr);
}
reader.close();
writer.close();
}/*bufferIO*/publicvoidbufferIO()throwsFileNotFoundException, IOException {
BufferedInputStream bufferReader=newBufferedInputStream(newFileInputStream("D:\\test\\bufferio_in.txt"));
BufferedOutputStream bufferWriter=newBufferedOutputStream(newFileOutputStream("D:\\test\\bufferio_out.txt"));intc = -1;while((c = bufferReader.read()) != -1) {
bufferWriter.write(c);
}
bufferReader.close();
bufferWriter.close();
}
2、NIO的例子/*NIO*/publicvoidNIO()throwsFileNotFoundException, IOException {
FileInputStream fin=newFileInputStream("D:\\test\\nio_in.txt");
FileOutputStream fout=newFileOutputStream("D:\\test\\nio_out.txt");
FileChannel finChannel=fin.getChannel();
FileChannel foutChannel=fout.getChannel();
ByteBuffer buffer= ByteBuffer.allocate(512);while(finChannel.read(buffer) != 1)//读到缓存{
buffer.flip();//指针跳到缓存头foutChannel.write(buffer);
buffer.clear();//重置缓冲区}
fin.close();
fout.close();
}
3、NIO实现非阻塞服务java自1.4以后，加入了新IO特性NIO，NIO带来了non-blocking特性。
在之前的服务器处理模型中，在调用ServerSocket.accept()方法时，会一直阻塞到有客户端连接才会返回，每个客户端连接过来后，服务端都会accept一个新连接，接着启动一个线程去处理该客户端的请求。在这个新的线程中，也会在read()方法中阻塞，直到读取完数据。
这样会有什么问题呢？
阻塞导致大量线程资源被浪费；阻塞可导致大量的上下文切换，很多切换其实是无意义的
那么NIO是如何帮助我们解决这种问题的呢？
1). 由一个专门的线程来处理所有的 IO 事件，并负责分发。
2). 事件驱动机制：事件到的时候触发，而不是同步的去监视事件。
3). 线程通讯：线程之间通过 wait,notify 等方式通讯。保证每次上下文切换都是有意义的。减少无谓的线程切换。
服务端和客户端各自维护一个管理通道的对象，我们称之为selector，该对象能检测一个或多个通道 (channel) 上的事件。我们以服务端为例，如果服务端的selector上注册了读事件，某时刻客户端给服务端发送了一些数据，NIO的服务端会在selector中添加一个读事件。服务端的处理线程会轮询地访问selector，如果访问selector时发现有感兴趣的事件到达，则处理这些事件，如果没有感兴趣的事件到达，则处理线程会一直阻塞直到感兴趣的事件到达为止。
下面是一个NIO实现Server的例子
publicclassMultiPortEcho {PRivateintports[];privateByteBuffer echoBuffer = ByteBuffer.allocate(1024);publicMultiPortEcho(intports[])throwsIOException {this.ports =ports;
go();
}privatevoidgo()throwsIOException {//Create a new selectorSelector selector =Selector.open();//Open a listener on each port, and register each one with the selectorfor(inti = 0; i < ports.length; ++i) {
ServerSocketChannel ssc=ServerSocketChannel.open();
ssc.configureBlocking(false);
ServerSocket ss=ssc.socket();
InetSocketAddress address=newInetSocketAddress(ports[i]);
ss.bind(address);
SelectionKey key=ssc.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("Going to listen on " +ports[i]);
}while(true) {intnum =selector.select();
Set selectedKeys=selector.selectedKeys();
Iterator it=selectedKeys.iterator();while(it.hasNext()) {
SelectionKey key=(SelectionKey) it.next();if((key.readyOps() & SelectionKey.OP_ACCEPT) ==SelectionKey.OP_ACCEPT) {//Accept the new connectionServerSocketChannel ssc =(ServerSocketChannel) key.channel();
SocketChannel sc=ssc.accept();
sc.configureBlocking(false);//Add the new connection to the selectorSelectionKey newKey =sc.register(selector,SelectionKey.OP_READ);
it.remove();
System.out.println("Got connection from " +sc);
}elseif((key.readyOps() & SelectionKey.OP_READ) ==SelectionKey.OP_READ) {//Read the dataSocketChannel sc =(SocketChannel) key.channel();//Echo dataintbytesEchoed = 0;while(true) {
echoBuffer.clear();intr =sc.read(echoBuffer);if(r <= 0) {
break;
}
echoBuffer.flip();
sc.write(echoBuffer);
bytesEchoed+=r;
}
System.out.println("Echoed " + bytesEchoed + " from " +sc);
it.remove();
}
}
}
}staticpublicvoidmain(String args[])throwsException {intports[] = {1234,6765,7987};for(inti = 0; i < args.length; ++i) {
ports[i]=Integer.parseInt(args[i]);
}newMultiPortEcho(ports);
}
}
参考资料:
http://www.ibm.com/developerworks/cn/education/java/j-nio/j-nio.html#ibm-pcon
http://weixiaolu.iteye.com/blog/1479656