Fix concurrent modification exception

src/androidTest/java/org/tasks/jobs/JobQueueTest.java

@@ -164,6 +164,25 @@ public class JobQueueTest {
                 queue.getJobs());
     }
 
+    @Test
+    public void multipleOverduePeriodsLapsed() {
+        long now = currentTimeMillis();
+
+        queue.add(new Reminder(1, now, TYPE_DUE));
+        queue.add(new Reminder(2, now + ONE_MINUTE, TYPE_DUE));
+        queue.add(new Reminder(3, now + 2 * ONE_MINUTE, TYPE_DUE));
+
+        verify(jobManager).schedule(TAG, now);
+
+        Freeze.freezeAt(now + ONE_MINUTE).thawAfter(new Snippet() {{
+            queue.removeOverdueJobs();
+        }});
+
+        assertEquals(
+                singletonList(new Reminder(3, now + 2 * ONE_MINUTE, TYPE_DUE)),
+                queue.getJobs());
+    }
+
     @Test
     public void clearShouldCancelExisting() {
         queue.add(new Reminder(1, 1, 0));

src/main/java/org/tasks/jobs/JobQueue.java

@@ -1,6 +1,7 @@
 package org.tasks.jobs;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Ordering;
 import com.google.common.collect.TreeMultimap;
 import com.google.common.primitives.Longs;
@@ -8,6 +9,7 @@ import com.google.common.primitives.Longs;
 import org.tasks.preferences.Preferences;
 
 import java.util.List;
+import java.util.NavigableSet;
 import java.util.SortedSet;
 
 import static com.google.common.collect.Iterables.filter;
@@ -63,7 +65,7 @@ public class JobQueue<T extends JobQueueEntry> {
     public synchronized List<T> removeOverdueJobs() {
         List<T> result = newArrayList();
         SortedSet<Long> lapsed = jobs.keySet().headSet(currentTimeMillis() + 1);
-        for (Long key : lapsed) {
+        for (Long key : ImmutableSortedSet.copyOf(lapsed)) {
             result.addAll(jobs.removeAll(key));
         }
         return result;