Make SheepBouncer logic cancellable.

Following the changes in 96c1f18517, this commit makes SheepBouncer cancellable for the same reasons as outlined in the MASpawnThread commit.

src/main/java/com/garbagemule/MobArena/ArenaImpl.java

@@ -586,6 +586,7 @@ public class ArenaImpl implements Arena
         
         // Stop spawning.
         stopSpawner();
+        stopBouncingSheep();
 
         // Announce and clean arena floor, etc.
         if (settings.getBoolean("global-end-announce", false)) {
@@ -1030,15 +1031,24 @@ public class ArenaImpl implements Arena
         world.setSpawnFlags(allowMonsters, allowAnimals);
     }
     
-    private void startBouncingSheep()
-    {
-        // Create a new bouncer if necessary.
-        if (sheepBouncer == null) {
-            sheepBouncer = new SheepBouncer(this);
+    private void startBouncingSheep() {
+        if (sheepBouncer != null) {
+            sheepBouncer.stop();
+            sheepBouncer = null;
         }
-        
-        // Start bouncing!
-        scheduleTask(sheepBouncer, settings.getInt("first-wave-delay", 5) * 20);
+
+        sheepBouncer = new SheepBouncer(this);
+        sheepBouncer.start();
+    }
+
+    private void stopBouncingSheep() {
+        if (sheepBouncer == null) {
+            plugin.getLogger().warning("Can't stop non-existent sheep bouncer in arena " + configName() + ". This should never happen.");
+            return;
+        }
+
+        sheepBouncer.stop();
+        sheepBouncer = null;
     }
 
     @Override

src/main/java/com/garbagemule/MobArena/waves/SheepBouncer.java

@@ -1,9 +1,11 @@
 package com.garbagemule.MobArena.waves;
 
 import com.garbagemule.MobArena.framework.Arena;
+import org.bukkit.Bukkit;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.LivingEntity;
 import org.bukkit.entity.Player;
+import org.bukkit.scheduler.BukkitTask;
 
 import java.util.HashSet;
 import java.util.Set;
@@ -13,11 +15,34 @@ public class SheepBouncer implements Runnable
     public static final int BOUNCE_INTERVAL = 20;
     private Arena arena;
     private Set<LivingEntity> sheep;
+
+    private BukkitTask task;
     
     public SheepBouncer(Arena arena) {
         this.arena = arena;
     }
     
+    public void start() {
+        if (task != null) {
+            arena.getPlugin().getLogger().warning("Starting sheep bouncer in arena " + arena.configName() + " with existing bouncer still running. This should never happen.");
+            task.cancel();
+            task = null;
+        }
+
+        int delay = arena.getSettings().getInt("first-wave-delay", 5) * 20;
+        task = Bukkit.getScheduler().runTaskLater(arena.getPlugin(), this, delay);
+    }
+
+    public void stop() {
+        if (task == null) {
+            arena.getPlugin().getLogger().warning("Can't stop non-existent sheep bouncer in arena " + arena.configName() + ". This should never happen.");
+            return;
+        }
+
+        task.cancel();
+        task = null;
+    }
+
     @Override
     public void run() {
         // If the arena isn't running or has no players, bail out
@@ -63,7 +88,7 @@ public class SheepBouncer implements Runnable
         }
         
         // Reschedule for more bouncy madness!
-        arena.scheduleTask(this, BOUNCE_INTERVAL);
+        task = Bukkit.getScheduler().runTaskLater(arena.getPlugin(), this, BOUNCE_INTERVAL);
     }
     
     /*private boolean isTargetNearby(Creature c, LivingEntity t) {