WatchService vs. Apache Commons IO Mnitoring (#921)

* WatchService vs. Apache Commons IO Mnitoring

* Indentation fixed

core-java/src/main/java/com/baeldung/dirmonitoring/DirectoryMonitoringExample.java

@@ -0,0 +1,38 @@
+package com.baeldung.dirmonitoring;
+
+import java.io.File;
+
+import org.apache.commons.io.monitor.FileAlterationListener;
+import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
+import org.apache.commons.io.monitor.FileAlterationMonitor;
+import org.apache.commons.io.monitor.FileAlterationObserver;
+
+public class DirectoryMonitoringExample {
+
+    public static final int POLL_INTERVAL = 500;
+
+    public static void main(String[] args) throws Exception {
+        FileAlterationObserver observer = new FileAlterationObserver(System.getProperty("user.home"));
+        FileAlterationMonitor monitor = new FileAlterationMonitor(POLL_INTERVAL);
+        FileAlterationListener listener = new FileAlterationListenerAdaptor() {
+            @Override
+            public void onFileCreate(File file) {
+                System.out.println("File: " + file.getName() + " created");
+            }
+
+            @Override
+            public void onFileDelete(File file) {
+                System.out.println("File: " + file.getName() + " deleted");
+            }
+
+            @Override
+            public void onFileChange(File file) {
+                System.out.println("File: " + file.getName() + " changed");
+            }
+        };
+        observer.addListener(listener);
+        monitor.addObserver(observer);
+        monitor.start();
+
+    }
+}