What does nio mean in java?

NIO in Java is a non-blocking API for asynchronous I/O operations. Its advantages include: Non-blocking: improves concurrency and allows threads to perform other tasks without waiting for I/O Finish. High performance: Use overlapping I/O to maximize system resource utilization. Scalability: Supports large-scale concurrent connections.

NIO in Java

NIO, that is, N on-IOcking Overlapped I/O (non-blocking overlapped I/O) is an asynchronous I/O operation in Java API.

How NIO works

Traditional I/O operations are blocking, which means that the thread will pause execution before the data is ready. NIO adopts a non-blocking method, and threads can continue to perform other tasks without waiting for the I/O operation to complete.

When the data is ready, NIO will notify the thread through the event notification mechanism. Threads can register a callback function that will be called when data is ready.

Benefits of NIO

• Non-blocking: NIO allows threads to perform other tasks without waiting for I/O operations to complete. This improves application concurrency.
• High performance: NIO uses overlapped I/O, which means it can perform multiple I/O operations at the same time to maximize the use of system resources.
• Scalability: NIO supports large-scale concurrent connections, making it ideal for applications that handle large amounts of I/O operations.

Usage of NIO

In order to use NIO, you need to create a Selector object that is responsible for monitoring multiple channels (e.g. Socket or FileChannel). Channels can be registered to be interested in specific events such as reads or writes.

When an event occurs, the Selector will notify the program through the SelectionKey object. SelectionKey contains information about the event type and related channels.

NIO example

The following is a code example that uses NIO to handle client requests on the server:

<code class="java">import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class EchoServer {

    public static void main(String[] args) throws Exception {
        ServerSocketChannel serverChannel = ServerSocketChannel.open();
        Selector selector = Selector.open();

        serverChannel.configureBlocking(false);
        serverChannel.register(selector, SelectionKey.OP_ACCEPT);

        while (true) {
            selector.select();
            Set<SelectionKey> selectedKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectedKeys.iterator();

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

                if (key.isAcceptable()) {
                    SocketChannel clientChannel = serverChannel.accept();
                    clientChannel.configureBlocking(false);
                    clientChannel.register(selector, SelectionKey.OP_READ);
                }
                else if (key.isReadable()) {
                    // 处理客户端请求...
                }

                iterator.remove();
            }
        }
    }
}</code>

This code creates a server , which uses NIO to receive and process client requests non-blockingly, thereby improving application concurrency.

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