如何解决Java错误，从内部类引用的局部变量必须是final或有效的final？

Question

我在代码行中收到错误“从内部类引用的局部变量必须是最终的或实际上是最终的”

newscrollPanel = new JScrollPane(newList);

我在staffPanel构造函数中将newscrollPanel贴花了。

Id希望能够在同一位置添加newscrollPanel变量，我添加其他GUI元素（请参见代码的底部），以便面板按名称显示在旁边。我发布的代码ive是我认为可以做到的方式，但是我收到开始时描述的错误。如果我将面板添加到sortbylastName操作侦听器中，则面板将显示在注销按钮后的末尾，该按钮为false（请参见此图片https://i.imgur.com/sh28fbX.png）。图片。我怎样才能做到这一点？谢谢

public class staffPanel {

    private JPanel Panel = new JPanel(new GridLayout(0, 2, 0, 15));

    public staffPanel(User userInput, UserManagement managementDatabase) {
        JButton getName = new JButton("Show your full name");
        JButton changePassword = new JButton("Change your password");
        JButton updatefullName = new JButton("Update your full name and position");
        JButton sortbylastName = new JButton("Sort by last name");
        JButton LogOut = new JButton("Log out");
        JButton searchButton = new JButton("Search");



        JTextField oldPassword = new JTextField();
        JTextField newPassword = new JTextField();
        JTextField firstName = new JTextField();
        JTextField lastName = new JTextField();
        JTextField position = new JTextField();
        JTextField searchBar = new JTextField("Search User");

        JLabel usersfullName = new JLabel();
        JLabel spacer;
        JLabel oldpasswordLabel = new JLabel("Old password");
        JLabel newpasswordLabel = new JLabel("New password");
        JLabel firstnameLabel = new JLabel("First name");
        JLabel lastnameLabel = new JLabel("Last name");
        JLabel positionLabel = new JLabel("Position");

          JScrollPane newscrollPanel;


        getName.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent clicked) {
                usersfullName.setText(getFullName(userInput));
            }
        });

        LogOut.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JFrame mainFrame = (JFrame) SwingUtilities.getWindowAncestor(Panel);
                Panel.setSize(400, 100);
                Panel.setVisible(false);
                userLogin newLogin = new userLogin(managementDatabase);
                mainFrame.add(newLogin.getPanel());
            }
        });

        changePassword.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent clicked) {

                boolean result = (managementDatabase.changePassword(userInput.getUserName(), oldPassword.getText(), newPassword.getText()));

                if (result == true) {
                    JOptionPane.showMessageDialog(null, "Password Sucessfully Channged");
                } else {
                    JOptionPane.showMessageDialog(null, "Passowrd cannot be changed ", "ERROR", JOptionPane.ERROR_MESSAGE);
                }
            }
        });

        updatefullName.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent clicked) {

                if (firstName.getText().isEmpty() || lastName.getText().isEmpty()) {

                    JOptionPane.showMessageDialog(null, "username or password field empty!", "ERROR", JOptionPane.ERROR_MESSAGE);
                } else {

                    Staff newStaff = (Staff) userInput;
                    newStaff.setPoistion(position.getText());
                    userInput.setFirstName(firstName.getText());
                    userInput.setLastName(lastName.getText());
                    JOptionPane.showMessageDialog(null, "Username updated");

                }
            }
        });

        sortbylastName.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent clicked) {

                List<Customer> customerList;
                JList<String> newList;
                customerList = Customer.filterOnlyCustomerList(managementDatabase.getList());
                List<String> sortedList = customerList.stream().flatMap(e -> Stream.of(e.getFullName() + " " + e.getCustomerAddress())).sorted().collect(Collectors.toList());
                newList = new JList<>(sortedList.toArray(new String[sortedList.size()]));
                newscrollPanel = new JScrollPane(newList);
                Panel.add(newscrollPanel);
        }
        }
        );

        Panel.add(getName);

        Panel.add(usersfullName);

        Panel.add(changePassword);

        Panel.add(
                new JLabel());
        Panel.add(oldpasswordLabel);

        Panel.add(newpasswordLabel);

        Panel.add(oldPassword);

        Panel.add(newPassword);

        Panel.add(updatefullName);

        Panel.add(
                new JLabel());
        Panel.add(firstnameLabel);

        Panel.add(lastnameLabel);

        Panel.add(firstName);

        Panel.add(lastName);

        Panel.add(positionLabel);

        Panel.add(position);

        Panel.add(sortbylastName);

        Panel.add(spacer = new JLabel(" "));

        Panel.add(searchButton);

        Panel.add(searchBar);

        Panel.setVisible(
                true);
        Panel.add(LogOut);
        ;
    }

    public JPanel getPanel() {
        return Panel;
    }

    public String getFullName(User input) {
        return input.getFullName();
    }

}