Java中的fileSystemWatcher的建议/示例代码

import java.io.IOException;
import java.nio.file.*;
import static java.nio.file.StandardWatchEventKinds.*;

public class FileSystemWatcherExample {

    public static void main(String[] args) throws IOException {
        Path dir = Paths.get("/path/to/watch");
        try (WatchService watchService = FileSystems.getDefault().newWatchService()) {
            registerAll(dir, watchService);
            System.out.println("Watch Service started.");
            while (true) {
                WatchKey key;
                try {
                    key = watchService.take();
                } catch (InterruptedException e) {
                    return;
                }
                for (WatchEvent<?> event : key.pollEvents()) {
                    WatchEvent.Kind<?> kind = event.kind();
                    if (kind == OVERFLOW) {
                        continue;
                    }
                    WatchEvent<Path> ev = (WatchEvent<Path>) event;
                    Path filename = ev.context();
                    Path child = dir.resolve(filename);
                    System.out.println(kind + " - " + child);
                }
                boolean valid = key.reset();
                if (!valid) {
                    break;
                }
            }
        }
    }

    private static void registerAll(final Path start, final WatchService watcher) throws IOException {
        Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                    throws IOException
            {
                register(dir, watcher);
                return FileVisitResult.CONTINUE;
            }
        });
    }

    private static void register(Path dir, WatchService watcher) throws IOException {
        WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
    }
}