Method poll

ZezeJava/ZezeJava/src/main/java/Zeze/Collections/Queue.java:254–278

删除并返回头节点中的首个值 @return 头节点的首个值，null if empty

()

	 * @return 头节点的首个值，null if empty
	 */
	public V poll() {
		var root = getRoot();
		if (root == null)
			return null;

		var headKey = root.getHeadNodeKey();
		if (headKey.getNodeId() == 0)
			return null;

		var head = getNode(headKey);
		if (head == null)
			return null;

		var nodeValues = head.getValues();
		var nodeValue = nodeValues.remove(0);
		root.setCount(root.getCount() - 1);
		if (nodeValues.isEmpty()) {
			root.setHeadNodeKey(head.getNextNodeKey());
			module._tQueueNodes.remove(headKey);
		}

		@SuppressWarnings("unchecked")
		var value = (V)nodeValue.getValue().getBean();
		return value;
	}

	/**
	 * @return 头节点的首个值，null if empty