所以我尝试用checkindoubleroom方法建立一个酒店：这个方法在availabledoubleroomsvector中查找一个可用的双人房，将其状态更改为“已占用”，并将其放入“已占用房间”树中。但是，将其插入此树会产生错误（错误总是以粗体显示）。

public int checkInDoubleRoom(int clientId) {
        //x will store the roomid so it can be assigned to a client
        Comparable room_id = 0;
        //Look for a DoubleRoom in availableRooms
        //Search in availableRooms should be << O(n) if we assume that Family Rooms and Double Rooms get added randomly when they are 'READY'.
        for (int i = 0; i < availableRooms.size(); i++) { 
            if (availableRooms.get(i) instanceof DoubleRoom) {
                Room room_get = (Room)(availableRooms.get(i));
                //Room_get is a double room
                room_get.setStatus("OCCUPIED");
                room_id = room_get.getId();
                //Then put this room in the tree of non- Ready rooms
              **rooms.insert(room_get);**
                //find the client in the client tree with the right id: assign the room to the client
                Object a = clients.get(clientId);
                //TODO wtf this is wrong af
//          for (int j = 0; j < clients.depth(); j++) {
//              Object a = clients.get(j);
                ((Client)(a)).setRoom((int)room_id);    
            }

我在树中插入内容的代码如下所示：（这里我们在树中插入doubleroom（扩展room类的类）

public void insert(Comparable element)
    {
        insertAtNode(element,root,null);
    }   

    // we traverse the tree.
    // Current holds the pointer to the TreeNode we are currently checking
    // Parent holds the pointer to the parent of the current TreeNode
    private void insertAtNode(Comparable element,TreeNode current,TreeNode parent)
    {
        // if the node we check is empty: empty tree
        if(current == null)
        {
            TreeNode newNode = new TreeNode(element);
            // the current node is empty, but we have a parent
            if(parent != null)
            {
                // do we add it to the left?
                if(element.compareTo(parent.getValue()) < 0)
                {
                    parent.leftNode = newNode;
                }
                // or do we add it to the right?
                else
                {
                    parent.rightNode = newNode;
                }
            }
            // the current node is empty and it has no parent, we actually have an empty tree
            else root = newNode;
        }

      **else if(current.compareTo(element) == 0) {**
            System.out.println("The element is already in the tree");
            // if the element is already in the tree, what to do?
        }
        // if the element is smaller than current, go left
        else if(current.compareTo(element) < 0)
        {
            insertAtNode(element,current.getLeftTree(),current);
        }
        // if the element is bigger than current, go right
        else insertAtNode(element,current.getRightTree(),current);
    }

然后，compareto方法将我们带到树类compareto方法：

public int compareTo(Object o) {
        if (o instanceof Integer) {
            return value.compareTo(o);
        } 
        else if (o instanceof TreeNode) {
            TreeNode node = ( TreeNode )o;
            return value.compareTo(node.value);
        } 
        else if (o instanceof Object){
          **return value.compareTo(o);**
        }
        else {
            throw new IllegalArgumentException();
        }}

我试图将treenode的值（应该是room类的示例）与room对象进行比较，但是它抛出了错误

"lass mainPackage.DoubleRoom cannot be cast to class java.lang.Integer (mainPackage.DoubleRoom is in unnamed module of loader 'app'; java.lang.Integer is in module java.base of loader 'bootstrap')
    at java.base/java.lang.Integer.compareTo(Integer.java:64)"

但我不明白为什么用整数。比较？？
编辑：完成堆栈跟踪：

Exception in thread "main" java.lang.ClassCastException: class mainPackage.DoubleRoom cannot be cast to class java.lang.Integer (mainPackage.DoubleRoom is in unnamed module of loader 'app'; java.lang.Integer is in module java.base of loader 'bootstrap')
    at java.base/java.lang.Integer.compareTo(Integer.java:64)
    at importedClass.Tree$TreeNode.compareTo(Tree.java:73)
    at importedClass.Tree.insertAtNode(Tree.java:202)
    at importedClass.Tree.insert(Tree.java:172)
    at mainPackage.HotelManagement.checkInDoubleRoom(HotelManagement.java:94)
    at mainPackage.Main.main(Main.java:37)

提前谢谢！