面试题：自定义Java处理流以极致提升特定场景下的IO性能

设计思路

缓冲区设计：使用较大的缓冲区来减少网络读取和文件写入的次数。对于网络读取，设置一个合适大小的缓冲区，减少网络I/O的频繁调用。对于文件写入，同样使用缓冲区，减少磁盘I/O次数。
异步处理：利用Java的异步I/O特性，在数据读取到缓冲区后，异步地进行数据校验和预处理，这样可以在等待网络数据或文件写入的同时进行处理，提高整体效率。
线程池管理：为异步处理的数据校验和预处理任务创建一个线程池，避免频繁创建和销毁线程带来的开销。

关键代码片段

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class CustomProcessingStream extends FilterOutputStream {
    private static final int BUFFER_SIZE = 8192;
    private final ExecutorService executorService;
    private final AsynchronousSocketChannel socketChannel;
    private final ByteBuffer readBuffer;
    private final ByteBuffer writeBuffer;
    private final FileChannel fileChannel;

    public CustomProcessingStream(OutputStream out, AsynchronousSocketChannel socketChannel, String filePath) throws IOException {
        super(out);
        this.socketChannel = socketChannel;
        this.readBuffer = ByteBuffer.allocate(BUFFER_SIZE);
        this.writeBuffer = ByteBuffer.allocate(BUFFER_SIZE);
        this.fileChannel = FileChannel.open(Paths.get(filePath), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
        this.executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
    }

    @Override
    public void write(int b) throws IOException {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    public void processData() throws IOException {
        while (true) {
            readBuffer.clear();
            socketChannel.read(readBuffer).get();
            readBuffer.flip();
            executorService.submit(() -> {
                try {
                    byte[] data = new byte[readBuffer.remaining()];
                    readBuffer.get(data);
                    // 进行数据校验和预处理
                    byte[] processedData = preprocessData(data);
                    writeBuffer.clear();
                    writeBuffer.put(processedData);
                    writeBuffer.flip();
                    fileChannel.write(writeBuffer);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }
    }

    private byte[] preprocessData(byte[] data) {
        // 复杂的数据校验和预处理逻辑
        // 这里简单示例，实际需替换为真实逻辑
        return data;
    }

    @Override
    public void close() throws IOException {
        executorService.shutdown();
        socketChannel.close();
        fileChannel.close();
        super.close();
    }
}

使用示例：

import java.io.FileOutputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.AsynchronousSocketChannel;

public class Main {
    public static void main(String[] args) {
        try (AsynchronousSocketChannel socketChannel = AsynchronousSocketChannel.open();
             FileOutputStream fileOutputStream = new FileOutputStream("output.txt");
             CustomProcessingStream customStream = new CustomProcessingStream(fileOutputStream, socketChannel, "output.txt")) {
            socketChannel.connect(new InetSocketAddress("localhost", 12345)).get();
            customStream.processData();
        } catch (IOException | InterruptedException | java.util.concurrent.ExecutionException e) {
            e.printStackTrace();
        }
    }
}

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面试题：自定义Java处理流以极致提升特定场景下的IO性能

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设计思路

关键代码片段