[astro] Tidy up set of scheduled futures (#3811)

...in order to not keep useless references to finished jobs in the collections.

It's taking the opportunity for tyding up every time a new job gets scheduled.
In that way, the job's runnables don't have to be cluttered with these
internals of the handler.

Signed-off-by: Simon Kaufmann <simon.kfm@googlemail.com>

extensions/binding/org.eclipse.smarthome.binding.astro/src/main/java/org/eclipse/smarthome/binding/astro/handler/AstroThingHandler.java

@@ -16,6 +16,7 @@
 import java.util.Calendar;
 import java.util.Date;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.Set;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
@@ -278,6 +279,7 @@ public void schedule(Job job, Calendar eventAt) {
         long sleepTime;
         monitor.lock();
         try {
+            tidyScheduledFutures();
             sleepTime = eventAt.getTimeInMillis() - new Date().getTime();
             ScheduledFuture<?> future = scheduler.schedule(job, sleepTime, TimeUnit.MILLISECONDS);
             scheduledFutures.add(future);
@@ -290,6 +292,16 @@ public void schedule(Job job, Calendar eventAt) {
         }
     }
 
+    private void tidyScheduledFutures() {
+        for (Iterator<ScheduledFuture<?>> iterator = scheduledFutures.iterator(); iterator.hasNext();) {
+            ScheduledFuture<?> future = iterator.next();
+            if (future.isDone()) {
+                logger.trace("Tidying up done future {}", future);
+                iterator.remove();
+            }
+        }
+    }
+
     /**
      * Calculates and publishes the daily Astro data.
      */