try (InputStream in = new FileInputStream("in.bin");
     OutputStream out = new FileOutputStream("out.bin")) {
    byte[] buf = new byte[8192];
    int n;
    while ((n = in.read(buf)) != -1) out.write(buf, 0, n);
}

try (BufferedReader br = Files.newBufferedReader(Path.of("data.txt"))) {
    br.lines().forEach(System.out::println);
}

class Person implements Serializable { String name; transient int age; }
try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("p.bin"))) {
    oos.writeObject(new Person());
}

try (FileChannel ch = FileChannel.open(Path.of("file.txt"))) {
    ByteBuffer buf = ByteBuffer.allocate(1024);
    ch.read(buf);
    buf.flip();
}

Path p = Path.of("logs/app.log");
Files.createDirectories(p.getParent());
Files.writeString(p, "hello\n", StandardOpenOption.CREATE, StandardOpenOption.APPEND);

Files.walk(Path.of("."))
     .filter(Files::isRegularFile)
     .forEach(System.out::println);

WatchService ws = FileSystems.getDefault().newWatchService();
Path dir = Path.of("inbox");
dir.register(ws, StandardWatchEventKinds.ENTRY_CREATE);
WatchKey key = ws.take();