1 files changed, 5 insertions, 6 deletions

diff --git a/subprojects/store-dse/src/main/java/tools/refinery/store/dse/transition/statespace/internal/ObjectivePriorityQueueImpl.java b/subprojects/store-dse/src/main/java/tools/refinery/store/dse/transition/statespace/internal/ObjectivePriorityQueueImpl.java
index c88a411f..2f3e142a 100644
--- a/subprojects/store-dse/src/main/java/tools/refinery/store/dse/transition/statespace/internal/ObjectivePriorityQueueImpl.java
+++ b/subprojects/store-dse/src/main/java/tools/refinery/store/dse/transition/statespace/internal/ObjectivePriorityQueueImpl.java
@@ -9,7 +9,6 @@ import tools.refinery.store.dse.transition.ObjectiveValues;
 import tools.refinery.store.dse.transition.VersionWithObjectiveValue;
 import tools.refinery.store.dse.transition.objectives.Objective;
 import tools.refinery.store.dse.transition.statespace.ObjectivePriorityQueue;
-import tools.refinery.store.map.Version;
 
 import java.util.Comparator;
 import java.util.List;
@@ -37,27 +36,27 @@ public class ObjectivePriorityQueueImpl implements ObjectivePriorityQueue {
         }
 
         @Override
-        public void submit(VersionWithObjectiveValue versionWithObjectiveValue) {
+        public synchronized void submit(VersionWithObjectiveValue versionWithObjectiveValue) {
                 priorityQueue.add(versionWithObjectiveValue);
         }
 
         @Override
-        public void remove(VersionWithObjectiveValue versionWithObjectiveValue) {
+        public synchronized void remove(VersionWithObjectiveValue versionWithObjectiveValue) {
                 priorityQueue.remove(versionWithObjectiveValue);
         }
 
         @Override
-        public int getSize() {
+        public synchronized int getSize() {
                 return priorityQueue.size();
         }
 
         @Override
-        public VersionWithObjectiveValue getBest() {
+        public synchronized VersionWithObjectiveValue getBest() {
                 return priorityQueue.peek();
         }
 
         @Override
-        public VersionWithObjectiveValue getRandom(Random random) {
+        public synchronized VersionWithObjectiveValue getRandom(Random random) {
                 int randomPosition = random.nextInt(getSize());
                 for (VersionWithObjectiveValue entry : this.priorityQueue) {
                         if (randomPosition-- == 0) {