added a SingletonTrait to reduce code duplication

src/block/BlockFactory.php

@@ -51,6 +51,7 @@ use pocketmine\block\utils\TreeType;
 use pocketmine\item\Item;
 use pocketmine\item\ItemIds;
 use pocketmine\item\ToolTier;
+use pocketmine\utils\SingletonTrait;
 use function array_fill;
 use function array_filter;
 use function get_class;
@@ -60,15 +61,7 @@ use function min;
  * Manages block registration and instance creation
  */
 class BlockFactory{
-	/** @var self|null */
-	private static $instance = null;
-
-	public static function getInstance() : self{
-		if(self::$instance === null){
-			self::$instance = new self;
-		}
-		return self::$instance;
-	}
+	use SingletonTrait;
 
 	/**
 	 * @var \SplFixedArray|Block[]

src/item/ItemFactory.php

@@ -33,6 +33,7 @@ use pocketmine\entity\EntityFactory;
 use pocketmine\entity\Living;
 use pocketmine\inventory\ArmorInventory;
 use pocketmine\nbt\tag\CompoundTag;
+use pocketmine\utils\SingletonTrait;
 use function constant;
 use function defined;
 use function explode;
@@ -46,15 +47,7 @@ use function trim;
  * Manages Item instance creation and registration
  */
 class ItemFactory{
-	/** @var self|null */
-	private static $instance = null;
-
-	public static function getInstance() : self{
-		if(self::$instance === null){
-			self::$instance = new self;
-		}
-		return self::$instance;
-	}
+	use SingletonTrait;
 
 	/** @var Item[] */
 	private $list = [];

src/utils/SingletonTrait.php

@@ -0,0 +1,44 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\utils;
+
+trait SingletonTrait{
+	/** @var self|null */
+	private static $instance = null;
+
+	private static function make() : self{
+		return new self;
+	}
+
+	public static function getInstance() : self{
+		if(self::$instance === null){
+			self::$instance = self::make();
+		}
+		return self::$instance;
+	}
+
+	public static function reset() : void{
+		self::$instance = null;
+	}
+}