Which Operating Systems support native (inotify-like) file watching in Java

Question

The JavaDoc for java.nio.file.WatchService states;

The implementation ... is intended to map directly on to the native file eve

Answer 1

This should have probably been a comment, but it's too big to post it as such...

I am looking at jdk-9 sources (could easily be searched in the jdk-8 repo as well), but here is some relevant to your question comments:

   /**
     * Linux implementation of WatchService based on inotify.
     *
     * In summary a background thread polls inotify plus a socket used for the wakeup
     * mechanism. Requests to add or remove a watch, or close the watch service,
     * cause the thread to wakeup and process the request. Events are processed
     * by the thread which causes it to signal/queue the corresponding watch keys.
     */

 class LinuxWatchService  extends AbstractWatchService

And for windows:

/*
 * Win32 implementation of WatchService based on ReadDirectoryChangesW.
 */

class WindowsWatchService extends AbstractWatchService

And so on.. you can find all the available implementations under:

 jdk/src/java.base/{windows|unix|solaris|linux...}/classes/sun/nio/fs/

As what OS actually supports this, it seems like that would require for you to look at the actual distro.