By what mechanisms does NIO provide non-blocking access to resources?

NIO provides non-blocking access to resources through the following mechanisms:

• Channels: These are bidirectional connections between a buffer and an entity capable of performing I/O operations (e.g., a file or network socket). Channels can be either blocking or non-blocking.
• Buffers: Containers for storing data of fixed size. I/O operations are performed between channels and buffers.
• Selectors: Allow a single thread to handle multiple channels. A selector can "listen" for readiness events on registered channels (e.g., ready for reading or writing) and notify the thread when they occur.

// Example of using a Selector for non-blocking reading from a SocketChannel
Selector selector = Selector.open();
SocketChannel channel = SocketChannel.open(new InetSocketAddress("localhost", 8080));
channel.configureBlocking(false); // Set non-blocking mode
channel.register(selector, SelectionKey.OP_READ); // Register channel for read event

// Loop waiting for channels to be ready
while (selector.select() > 0) {
    Set<SelectionKey> selectedKeys = selector.selectedKeys();
    Iterator<SelectionKey> keyIterator = selectedKeys.iterator();

    while (keyIterator.hasNext()) {
        SelectionKey key = keyIterator.next();

        if (key.isReadable()) {
            // Channel is ready for reading
            SocketChannel socketChannel = (SocketChannel) key.channel();
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            socketChannel.read(buffer);
            buffer.flip();
            // Process data from buffer
        }
        keyIterator.remove();
    }
}