SPIGOT-2623: Add EntityEquipment methods to get/set ItemStacks by slot.

src/main/java/org/bukkit/craftbukkit/inventory/CraftEntityEquipment.java

@@ -1,10 +1,13 @@
 package org.bukkit.craftbukkit.inventory;
 
+import com.google.common.base.Preconditions;
 import net.minecraft.server.EntityInsentient;
 import net.minecraft.server.EnumItemSlot;
+import org.bukkit.craftbukkit.CraftEquipmentSlot;
 import org.bukkit.craftbukkit.entity.CraftLivingEntity;
 import org.bukkit.entity.Entity;
 import org.bukkit.inventory.EntityEquipment;
+import org.bukkit.inventory.EquipmentSlot;
 import org.bukkit.inventory.ItemStack;
 
 public class CraftEntityEquipment implements EntityEquipment {
@@ -15,6 +18,20 @@ public class CraftEntityEquipment implements EntityEquipment {
         this.entity = entity;
     }
 
+    @Override
+    public void setItem(EquipmentSlot slot, ItemStack item) {
+        Preconditions.checkArgument(slot != null, "slot must not be null");
+        EnumItemSlot nmsSlot = CraftEquipmentSlot.getNMS(slot);
+        setEquipment(nmsSlot, item);
+    }
+
+    @Override
+    public ItemStack getItem(EquipmentSlot slot) {
+        Preconditions.checkArgument(slot != null, "slot must not be null");
+        EnumItemSlot nmsSlot = CraftEquipmentSlot.getNMS(slot);
+        return getEquipment(nmsSlot);
+    }
+
     @Override
     public ItemStack getItemInMainHand() {
         return getEquipment(EnumItemSlot.MAINHAND);