如何通知线程更改

Question

I have created a class FolderObserver which observes a folder in my project for changes (file created/file deleted). My class is implementing the Runnable interface (I'm using the classes FileAlterationObserver, FileAlterationMonitor, FileAlterationListener from apache commons).

In my main class I start a thread with my FolderObserver object as an argument. What I would like to know is, how can I notify my thread on the changes that have occured? For example when a new file has been created in my folder.

This is my class FolderObserver:

public class FolderObserver implements Runnable {

private final String DIR = "server/scripts/gremlin-groovy/calculations/";

final long pollingInterval = 5000L;
private File folder;
private FileAlterationObserver observer;
private FileAlterationMonitor monitor;
private FileAlterationListener listener;



public FolderObserver()
{

    System.out.println("Creating Runnable");
    folder = new File(DIR);
    observer = new FileAlterationObserver(folder);
    monitor = new FileAlterationMonitor(pollingInterval);
}

@Override
public void run() {

    System.out.println("Thread is running");
    listener = new FileAlterationListenerAdaptor() {
            // Is triggered when a file is created in the monitored folder
            @Override
            public void onFileCreate(File file) {
                try {
                    // "file" is the reference to the newly created file

                    System.out.println("Created file : " + file.getCanonicalPath());

                } catch (IOException e) {

                }
            }

            // Is triggered when a file is deleted from the monitored folder
            @Override
            public void onFileDelete(File file) {

                try {
                    // "file" is the reference to the removed file

                    System.out.println("Removed file : " + file.getCanonicalPath());


                    //logger.log(LogLevel.DEBUG,logId,"File exists in location '{}'",bool);
                } catch (IOException e) {
                    //logger.log(LogLevel.ERROR, "Received IOException '{}' when trying to remove file", e.toString());

                }
            }
        };
        observer.addListener(listener);
        monitor.addObserver(observer);
        try {
            monitor.start();
            System.out.println("Monitor started");
            //logger.log(LogLevel.DEBUG,logId,"Monitor started");
        } catch (Exception e) {
            //logger.log(LogLevel.ERROR, "Received Exception '{}' when trying to start monitor", e.toString());
        }
}

   }

This is how I create and start the thread from my main class:

  FolderObserver observer = new FolderObserver();
  Thread t = new Thread(observer);
  t.start();

Answer 1

You create a inner interface inside your FolderObserver .

public interface MyTrueObserver(){
   public void notifySmthChanged();
}

You can now implement that class in your main class by doing

public class MyMainClass implements MyTrueObserver()

There you define the interface method

public void notifySmthChanged(){
// I got called Do smth!
}

Lastly, you reference your thread the main class.

And call it here

@Override
public void onFileCreate(File file) {
               referenceObjectToMainClass.notifySmthChanged();
            }