尝试使用数据库中的整数值填充JComboBox。代码有什么问题？

Question

我正在建立一个图书馆管理系统。我在问题表中将book_ID值设置为int。如何将它们添加到comboBox。每个学生都有他的名字上有多本书。我想添加comboBox来选择要在返还书类中使用的特定书籍。

 JComboBox<Integer> bookID = new JComboBox<Integer>();
            bookID.addMouseListener(new MouseAdapter() {
                public void mousePressed(MouseEvent e) {
                    ArrayList<Integer> books  = new ArrayList<Integer>();
                    String query = "SELECT Book_ID FROM Issue where Student_ID=?";
                    try {
                        pst = conn.prepareStatement(query);
                        rs = pst.executeQuery(query);
                        while(rs.next()){
                            int id = rs.getInt("Book_ID");
                            books.add(id);
                        }
                        rs.close();
                    } catch (SQLException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }
                    // populate the combo box
                    DefaultComboBoxModel<Integer> model = new DefaultComboBoxModel<Integer>((Integer[]) books.toArray());
                    bookID.setModel(model);
                }
            });
            bookID.setBounds(467, 53, 163, 26);
            contentPane.add(bookID);