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package com.zetcode;

import java.io.IOException;

import java.nio.file.FileSystems;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.nio.file.WatchEvent;

import java.nio.file.WatchKey;

import java.nio.file.WatchService;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Future;

import java.util.concurrent.TimeUnit;

import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;

import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE;

import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;

public class DirWatcherThread implements Runnable {

private final Path dir;

private final WatchService watcher;

private final WatchKey key;

@SuppressWarnings("unchecked")

private static <T> WatchEvent<T> cast(WatchEvent<?> event) {

return (WatchEvent<T>) event;

}

public DirWatcherThread(Path dir) throws IOException {

this.dir = dir;

this.watcher = FileSystems.getDefault().newWatchService();

this.key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);

}

public void run() {

while (true) {

// wait for key to be signalled

WatchKey key;

try {

key = watcher.take();

} catch (InterruptedException e) {

return;

}

if (this.key != key) {

System.err.println("WatchKey not recognized!");

continue;

}

for (WatchEvent<?> event : key.pollEvents()) {

WatchEvent<Path> ev = cast(event);

System.out.format("%s: %s\n", ev.kind(), dir.resolve(ev.context()));

}

// reset key

key.reset();

}

}

public static void main(String[] args) throws IOException, InterruptedException {

Path dir = Paths.get("C:/Users/Jano/tmp/");

var watcher = new DirWatcherThread(dir);

ExecutorService executor = Executors.newSingleThreadExecutor();

Future<?> future = executor.submit(watcher);

// Shutdown after 20 seconds

executor.awaitTermination(20, TimeUnit.SECONDS);

// abort watcher

future.cancel(true);

executor.awaitTermination(1, TimeUnit.SECONDS);

executor.shutdownNow();

}

}