Cache entity constructors for a small performance optimization

src/main/java/net/minecraftforge/fml/common/registry/EntityEntry.java

@@ -18,9 +18,15 @@
  */
 package net.minecraftforge.fml.common.registry;
 
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+
+import com.google.common.base.Throwables;
+
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.EntityList;
 import net.minecraft.entity.EntityList.EntityEggInfo;
+import net.minecraft.world.World;
 import net.minecraftforge.fml.common.registry.IForgeRegistryEntry.Impl;
 
 public class EntityEntry extends Impl<EntityEntry>
@@ -28,11 +34,30 @@ public class EntityEntry extends Impl<EntityEntry>
     private Class<? extends Entity> cls;
     private String name;
     private EntityEggInfo egg;
+    private Constructor<?> ctr;
 
     public EntityEntry(Class<? extends Entity> cls, String name)
     {
         this.cls = cls;
         this.name = name;
+        init();
+    }
+
+    //Protected method, to make this optional, in case people subclass this to have a better factory.
+    protected void init()
+    {
+        try
+        {
+            this.ctr = this.cls.getConstructor(World.class);
+        }
+        catch (NoSuchMethodException e)
+        {
+            throw new RuntimeException("Invalid class " + this.cls + " no constructor taking " + World.class.getName());
+        }
+        catch (SecurityException e)
+        {
+            Throwables.propagate(e);
+        }
     }
 
     public Class<? extends Entity> getEntityClass(){ return this.cls; }
@@ -45,4 +70,17 @@ public class EntityEntry extends Impl<EntityEntry>
         if (this.getRegistryName() != null)
             EntityList.ENTITY_EGGS.put(this.getRegistryName(), egg);
     }
+
+    public Entity newInstance(World world)
+    {
+        try
+        {
+            return (Entity)this.ctr.newInstance(world);
+        }
+        catch (Exception e)
+        {
+            e.printStackTrace();
+            return null;
+        }
+    }
 }