Watch change in file

Watcher.java

import java.io.IOException;
import java.nio.file.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Observable;
import java.util.Observer;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.RunnableFuture;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Collectors;

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

public class Watcher implements Runnable {
    private final WatchService watcher;
    private WatchKey watchKey;

    private final Consumer<Path> consumer;

    private Watcher(Consumer<Path> consumer) throws IOException {
        this.consumer = consumer;
        watcher = FileSystems.getDefault().newWatchService();
    }

    public static Watcher create(Consumer<Path> consumer) throws IOException {
        return new Watcher(consumer);
    }

    public Watcher watchDirectory(Path directory) throws IOException {
        directory.register(watcher, ENTRY_CREATE, ENTRY_MODIFY);
        return this;
    }

    public List<Path> getModifiedFiles() throws Exception {
        watchKey = watcher.take();
        List<Path> modifiedPaths = watchKey.pollEvents().stream()
                .filter(onlyCreatedOrModifiedFiles())
                .map(watchEvent -> (WatchEvent<Path>) watchEvent)
                .map(pathEvent -> pathEvent.context())
                .collect(Collectors.toList());
        return modifiedPaths;
    }

    private Predicate<WatchEvent<?>> onlyCreatedOrModifiedFiles() {
        return watchEvent -> watchEvent.kind() == ENTRY_CREATE || watchEvent.kind() == ENTRY_MODIFY;
    }

    private boolean reinit() {
        return watchKey.reset();
    }

    @Override
    public void run() {
        try {
            do {
                getModifiedFiles().forEach(consumer);
            } while (reinit());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

`import java.io.IOException;
import java.nio.file.Paths;

/**

• Created by yannickgrenzinger on 26/02/2016.
  */
  public class Main {

  public static void main(String... arg) throws IOException, InterruptedException {
  Watcher watcher = Watcher.create(path -> System.out.println("Modified file : " + path));
  watcher.watchDirectory(Paths.get("/Users/yannickgrenzinger/Lab/code/ruby/"));
  Thread th = new Thread(watcher, "FileWatcher");
  th.start();
  }
  }
  `