Java I/O 深度解析与实战指南：文件操作、流、NIO全面掌握

java复制编辑try (FileInputStream fis = new FileInputStream("input.dat")) {
    byte[] buffer = new byte[1024];
    int bytesRead;
    while ((bytesRead = fis.read(buffer)) != -1) {
        // 处理字节
        System.out.println("读取了 " + bytesRead + " 字节");
    }
} catch (IOException e) {
    e.printStackTrace();
}

java复制编辑try (BufferedReader reader = new BufferedReader(new FileReader("input.txt"))) {
    String line;
    while ((line = reader.readLine()) != null) {
        System.out.println("读取行: " + line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

java复制编辑try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"))) {
    writer.write("Hello, Java I/O!");
    writer.newLine();
    writer.write("写入结束");
} catch (IOException e) {
    e.printStackTrace();
}

java复制编辑try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream("source.jpg"));
     BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("dest.jpg"))) {
    byte[] buffer = new byte[8192];
    int len;
    while ((len = bis.read(buffer)) != -1) {
        bos.write(buffer, 0, len);
    }
} catch (IOException e) {
    e.printStackTrace();
}

java复制编辑ByteBuffer buffer = ByteBuffer.allocate(1024);
buffer.put("Hello NIO".getBytes());
buffer.flip();  // 切换到读取模式

while (buffer.hasRemaining()) {
    System.out.print((char) buffer.get());
}

java复制编辑try (FileChannel inChannel = new FileInputStream("input.txt").getChannel();
     FileChannel outChannel = new FileOutputStream("output.txt").getChannel()) {
    ByteBuffer buffer = ByteBuffer.allocate(1024);

    while (inChannel.read(buffer) != -1) {
        buffer.flip();
        outChannel.write(buffer);
        buffer.clear();
    }
} catch (IOException e) {
    e.printStackTrace();
}

java复制编辑// 示例略，核心思想是通过 Selector 监听多个 Channel 的事件

java复制编辑Path path = Paths.get("test.txt");
List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);

java复制编辑if (!Files.exists(path)) {
    Files.createFile(path);
}

java复制编辑try (FileChannel source = FileChannel.open(Paths.get("large.iso"), StandardOpenOption.READ);
     FileChannel target = FileChannel.open(Paths.get("copy.iso"), StandardOpenOption.WRITE, StandardOpenOption.CREATE)) {
    long size = source.size();
    long transferred = 0;
    while (transferred < size) {
        transferred += source.transferTo(transferred, size - transferred, target);
    }
} catch (IOException e) {
    e.printStackTrace();
}