trying to fix bug 875 by using the same MarkPassings to decide hasFinished and grab the time points

java/com.sap.sailing.domain/src/com/sap/sailing/domain/base/impl/CourseImpl.java

@@ -44,7 +44,7 @@ public class CourseImpl extends NamedImpl implements Course {
     
     public CourseImpl(String name, Iterable<Waypoint> waypoints) {
         super(name);
-        lock = new ReentrantReadWriteLock();
+        lock = new ReentrantReadWriteLock(/* fair */ true); // if non-fair, course update may need to wait forever for many concurrent readers
         listeners = new HashSet<CourseListener>();
         this.waypoints = new ArrayList<Waypoint>();
         waypointIndexes = new HashMap<Waypoint, Integer>();

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/DynamicTrackedRaceImpl.java

@@ -378,7 +378,7 @@ public class DynamicTrackedRaceImpl extends TrackedRaceImpl implements
             NavigableSet<MarkPassing> markPassingsForCompetitor = getMarkPassings(competitor);
             synchronized (markPassingsForCompetitor) {
                 for (MarkPassing oldMarkPassing : markPassingsForCompetitor) {
-                    if(oldStartMarkPassing == null) {
+                    if (oldStartMarkPassing == null) {
                         oldStartMarkPassing = oldMarkPassing;
                     }
                     oldMarkPassings.put(oldMarkPassing.getWaypoint(), oldMarkPassing);

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/TrackedRaceImpl.java

@@ -856,9 +856,11 @@ public abstract class TrackedRaceImpl implements TrackedRace, CourseListener {
     public MarkPassing getMarkPassing(Competitor competitor, Waypoint waypoint) {
         final NavigableSet<MarkPassing> markPassings = getMarkPassings(competitor);
         if (markPassings != null) {
-            for (MarkPassing markPassing : markPassings) {
-                if (markPassing.getWaypoint() == waypoint) {
-                    return markPassing;
+            synchronized (markPassings) {
+                for (MarkPassing markPassing : markPassings) {
+                    if (markPassing.getWaypoint() == waypoint) {
+                        return markPassing;
+                    }
                 }
             }
         }

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/WindwardToGoComparator.java

@@ -10,6 +10,7 @@ import com.sap.sailing.domain.common.Distance;
 import com.sap.sailing.domain.common.NoWindError;
 import com.sap.sailing.domain.common.NoWindException;
 import com.sap.sailing.domain.common.TimePoint;
+import com.sap.sailing.domain.tracking.MarkPassing;
 import com.sap.sailing.domain.tracking.TrackedLeg;
 import com.sap.sailing.domain.tracking.TrackedLegOfCompetitor;
 
@@ -36,14 +37,21 @@ public class WindwardToGoComparator implements Comparator<TrackedLegOfCompetitor
         assert o1.getLeg() == o2.getLeg();
         try {
             int result;
-            if (o1.hasFinishedLeg(timePoint)) {
-                if (o2.hasFinishedLeg(timePoint)) {
-                    result = trackedLeg.getTrackedRace().getMarkPassing(o1.getCompetitor(), trackedLeg.getLeg().getTo()).getTimePoint().compareTo(
-                            trackedLeg.getTrackedRace().getMarkPassing(o2.getCompetitor(), trackedLeg.getLeg().getTo()).getTimePoint());
+            // To avoid having to synchronize on the competitors' mark passings, grab the decisive mark passings up front and
+            // derive hasStarted / hasFinished from them; this is redundant to TrackedLegOfCompetitor.hasStarted/hasFinished but
+            // avoids the heavy-weight synchronization-based "locking". It shall help avoid NPEs in case the mark passings
+            // for a competitor change after deciding hasFinished and grabbing the mark passing (see bug 875).
+            final MarkPassing o1MarkPassingForLegEnd = trackedLeg.getTrackedRace().getMarkPassing(o1.getCompetitor(), trackedLeg.getLeg().getTo());
+            final MarkPassing o2MarkPassingForLegEnd = trackedLeg.getTrackedRace().getMarkPassing(o2.getCompetitor(), trackedLeg.getLeg().getTo());
+            final boolean o1HasFinishedLeg = o1MarkPassingForLegEnd != null && o1MarkPassingForLegEnd.getTimePoint().compareTo(timePoint) <= 0;
+            final boolean o2HasFinishedLeg = o2MarkPassingForLegEnd != null && o2MarkPassingForLegEnd.getTimePoint().compareTo(timePoint) <= 0;
+            if (o1HasFinishedLeg) {
+                if (o2HasFinishedLeg) {
+                    result = o1MarkPassingForLegEnd.getTimePoint().compareTo(o2MarkPassingForLegEnd.getTimePoint());
                 } else {
                     result = -1; // o1 < o2 because o1 already finished the leg but o2 didn't
                 }
-            } else if (o2.hasFinishedLeg(timePoint)) {
+            } else if (o2HasFinishedLeg) {
                 result = 1; // o1 > o2 because o2 already finished the leg but o1 didn't
             } else {
                 // both didn't finish the leg yet; check which one has started: