NIO (Non-blocking Input/Output) in Java is a powerful library that provides efficient I/O operations
It allows you to build scalable network applications by enabling non-blocking operations and using buffers, channels, and selectors
Here are a few examples to illustrate the use of NIO in different applications:
Example 1: Reading a File using NIO
This example demonstrates how to read the contents of a file using NIO
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
public class NIOFileRead {
public static void main(String[] args) {
Path path = Paths.get("example.txt");
try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.READ)) {
ByteBuffer buffer = ByteBuffer.allocate(1024);
int bytesRead = fileChannel.read(buffer);
while (bytesRead != -1) {
buffer.flip();
while (buffer.hasRemaining()) {
System.out.print((char) buffer.get());
}
buffer.clear();
bytesRead = fileChannel.read(buffer);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}Example 2: Writing to a File using NIO
This example demonstrates how to write data to a file using NIO
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
public class NIOFileWrite {
public static void main(String[] args) {
Path path = Paths.get("example.txt");
String content = "Hello, NIO!";
try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
ByteBuffer buffer = ByteBuffer.allocate(1024);
buffer.put(content.getBytes());
buffer.flip();
fileChannel.write(buffer);
} catch (IOException e) {
e.printStackTrace();
}
}
}Example 3: Non-blocking Server using NIO
This example demonstrates how to create a simple non-blocking server using NIO
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
public class NIOServer {
public static void main(String[] args) {
try {
Selector selector = Selector.open();
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.bind(new InetSocketAddress("localhost", 8080));
serverSocketChannel.configureBlocking(false);
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
while (true) {
selector.select();
Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
if (key.isAcceptable()) {
ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
SocketChannel socketChannel = serverChannel.accept();
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_READ);
} else if (key.isReadable()) {
SocketChannel socketChannel = (SocketChannel) key.channel();
ByteBuffer buffer = ByteBuffer.allocate(256);
int bytesRead = socketChannel.read(buffer);
if (bytesRead == -1) {
socketChannel.close();
} else {
buffer.flip();
String message = new String(buffer.array()).trim();
System.out.println("Received: " + message);
buffer.clear();
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}Example 4: Non-blocking Client using NIO
This example demonstrates how to create a simple non-blocking client using NIO
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
public class NIOClient {
public static void main(String[] args) {
try {
Selector selector = Selector.open();
SocketChannel socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
socketChannel.connect(new InetSocketAddress("localhost", 8080));
socketChannel.register(selector, SelectionKey.OP_CONNECT);
while (true) {
selector.select();
Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
if (key.isConnectable()) {
SocketChannel channel = (SocketChannel) key.channel();
if (channel.isConnectionPending()) {
channel.finishConnect();
}
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_WRITE);
} else if (key.isWritable()) {
SocketChannel channel = (SocketChannel) key.channel();
ByteBuffer buffer = ByteBuffer.wrap("Hello from NIO Client".getBytes());
channel.write(buffer);
channel.close();
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}Summary
These examples cover basic file operations and network communication using NIO
The first two examples show how to read from and write to files, while the last two demonstrate how to create a non-blocking server and client
These are foundational examples that can be expanded upon to build more complex applications