fix for concurrent modification problems http://www.slightlymagic.net/forum/viewtopic.php?p=115820#p115820

note: copy to new arraylist does not help against comodification problem. The only known to me solution is use classes from java.util.concurrent
Playarea redraw timeout increased to 50ms

src/main/java/forge/FThreads.java

@@ -136,6 +136,15 @@ public class FThreads {
         getScheduledPool().schedule(inputUpdater, milliseconds, TimeUnit.MILLISECONDS);
     }
 
+    public static void delayInEDT(int milliseconds, final Runnable inputUpdater) {
+        Runnable runInEdt = new Runnable() {
+            @Override public void run() {
+                FThreads.invokeInEdtNowOrLater(inputUpdater);
+            }
+        };
+        delay(milliseconds, runInEdt);
+    }
+    
     public static String debugGetCurrThreadId() {
         return isEDT() ? "EDT" : Long.toString(Thread.currentThread().getId());
     }

src/main/java/forge/card/cardfactory/CardFactoryUtil.java

@@ -788,7 +788,7 @@ public class CardFactoryUtil {
      */
     public static List<Card> getActivateablesFromZone(final PlayerZone zone, final Player activator) {
 
-        Iterable<Card> cl = Lists.newArrayList(zone.getCards());
+        Iterable<Card> cl = zone.getCards(); // copy to new AL won't help here
 
         // Only check the top card of the library
         if (zone.is(ZoneType.Library)) {

src/main/java/forge/game/zone/Zone.java

@@ -23,6 +23,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Observable;
 import java.util.Observer;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 import forge.Card;
 import forge.Singletons;
@@ -42,7 +43,7 @@ public class Zone extends MyObservable implements IZone, Observer, java.io.Seria
     private static final long serialVersionUID = -5687652485777639176L;
 
     /** The cards. */
-    protected final transient List<Card> cardList = new ArrayList<Card>();
+    protected final transient List<Card> cardList = new CopyOnWriteArrayList<Card>();
     protected final transient List<Card> roCardList;
     protected final ZoneType zoneName;
     protected boolean update = true;

src/main/java/forge/view/arcane/PlayArea.java

@@ -503,17 +503,11 @@ public class PlayArea extends CardPanelContainer implements CardPanelMouseListen
     public void setupPlayZone() {
         boolean wasSet = wantRedraw.getAndSet(true);
         if(wasSet) return;
-        FThreads.invokeInEdtLater(new Runnable() {
+        FThreads.delayInEDT(50, new Runnable() { // postpone play area update per 50ms
             @Override
             public void run() {
-                try { // user won't notice, but the requests coming in that interval won't trigger re-draw
-                    Thread.sleep(20);
-                } catch (InterruptedException e) {
-                    e.printStackTrace();
-                } 
                 wantRedraw.set(false);
-                final List<Card> modelshot = new ArrayList<Card>(model); // I am afraid of ConcurrentModificationExceptions
+                setupPlayZone(model);
-                setupPlayZone(modelshot);
             }
         });
     }