Improve entity hierarchy by adding Mob interface.

src/main/java/org/bukkit/craftbukkit/entity/CraftAmbient.java

@@ -5,7 +5,7 @@ import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.entity.Ambient;
 import org.bukkit.entity.EntityType;
 
-public class CraftAmbient extends CraftLivingEntity implements Ambient {
+public class CraftAmbient extends CraftMob implements Ambient {
     public CraftAmbient(CraftServer server, EntityAmbient entity) {
         super(server, entity);
     }

src/main/java/org/bukkit/craftbukkit/entity/CraftCreature.java

@@ -3,28 +3,12 @@ package org.bukkit.craftbukkit.entity;
 import net.minecraft.server.EntityCreature;
 import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.entity.Creature;
-import org.bukkit.entity.LivingEntity;
 
-public class CraftCreature extends CraftLivingEntity implements Creature {
+public class CraftCreature extends CraftMob implements Creature {
     public CraftCreature(CraftServer server, EntityCreature entity) {
         super(server, entity);
     }
 
-    public void setTarget(LivingEntity target) {
-        EntityCreature entity = getHandle();
-        if (target == null) {
-            entity.setGoalTarget(null, null, false);
-        } else if (target instanceof CraftLivingEntity) {
-            entity.setGoalTarget(((CraftLivingEntity) target).getHandle(), null, false);
-        }
-    }
-
-    public CraftLivingEntity getTarget() {
-        if (getHandle().getGoalTarget() == null) return null;
-
-        return (CraftLivingEntity) getHandle().getGoalTarget().getBukkitEntity();
-    }
-
     @Override
     public EntityCreature getHandle() {
         return (EntityCreature) entity;

src/main/java/org/bukkit/craftbukkit/entity/CraftFlying.java

@@ -4,7 +4,7 @@ import net.minecraft.server.EntityFlying;
 import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.entity.Flying;
 
-public class CraftFlying extends CraftLivingEntity implements Flying {
+public class CraftFlying extends CraftMob implements Flying {
 
     public CraftFlying(CraftServer server, EntityFlying entity) {
         super(server, entity);

src/main/java/org/bukkit/craftbukkit/entity/CraftMob.java

@@ -0,0 +1,39 @@
+package org.bukkit.craftbukkit.entity;
+
+import net.minecraft.server.EntityInsentient;
+import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.entity.Mob;
+
+public abstract class CraftMob extends CraftLivingEntity implements Mob {
+    public CraftMob(CraftServer server, EntityInsentient entity) {
+        super(server, entity);
+    }
+
+    @Override
+    public void setTarget(LivingEntity target) {
+        EntityInsentient entity = getHandle();
+        if (target == null) {
+            entity.setGoalTarget(null, null, false);
+        } else if (target instanceof CraftLivingEntity) {
+            entity.setGoalTarget(((CraftLivingEntity) target).getHandle(), null, false);
+        }
+    }
+
+    @Override
+    public CraftLivingEntity getTarget() {
+        if (getHandle().getGoalTarget() == null) return null;
+
+        return (CraftLivingEntity) getHandle().getGoalTarget().getBukkitEntity();
+    }
+
+    @Override
+    public EntityInsentient getHandle() {
+        return (EntityInsentient) entity;
+    }
+
+    @Override
+    public String toString() {
+        return "CraftMob";
+    }
+}

src/main/java/org/bukkit/craftbukkit/entity/CraftSlime.java

@@ -4,10 +4,9 @@ import net.minecraft.server.EntitySlime;
 
 import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.entity.EntityType;
-import org.bukkit.entity.LivingEntity;
 import org.bukkit.entity.Slime;
 
-public class CraftSlime extends CraftLivingEntity implements Slime {
+public class CraftSlime extends CraftMob implements Slime {
 
     public CraftSlime(CraftServer server, EntitySlime entity) {
         super(server, entity);
@@ -21,20 +20,6 @@ public class CraftSlime extends CraftLivingEntity implements Slime {
         getHandle().setSize(size, true);
     }
 
-    @Override
-    public void setTarget(LivingEntity target) {
-        if (target == null) {
-            getHandle().setGoalTarget(null, null, false);
-        } else if (target instanceof CraftLivingEntity) {
-            getHandle().setGoalTarget(((CraftLivingEntity) target).getHandle(), null, false);
-        }
-    }
-
-    @Override
-    public LivingEntity getTarget() {
-        return getHandle().getGoalTarget() == null ? null : (LivingEntity)getHandle().getGoalTarget().getBukkitEntity();
-    }
-
     @Override
     public EntitySlime getHandle() {
         return (EntitySlime) entity;