DefaultListModel<String> listModel=new DefaultListModel<>();

这段代码是创建了一个默认的列表模型（`DefaultListModel`），该模型的元素类型为字符串（`String`）。

具体来说，代码中使用了泛型，即在 `DefaultListModel` 后面加上了 `<String>`，表示该列表模型中只能存储字符串类型的元素。

然后，使用 `new` 关键字创建了一个名为 `listModel` 的默认列表模型对象，并将其赋值给该变量。此时，`listModel` 是一个空的列表模型对象，还没有任何元素。

相关问题

java用列表框Jlist<Message>实现，可以根据消息状态进行筛选信息，可以根据消息信息内容部分匹配进行筛选，可以删除选中信息，可以删除全部信息。

好的，以下是用JList和DefaultListModel实现信息筛选和删除的代码：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;

public class MessageList extends JPanel implements ActionListener {
    private DefaultListModel<Message> listModel;
    private JList<Message> messageList;
    private JComboBox<String> statusComboBox;
    private JTextField filterTextField;
    private JButton deleteButton;
    private JButton deleteAllButton;

    public MessageList() {
        super(new BorderLayout());
        listModel = new DefaultListModel<>();
        messageList = new JList<>(listModel);
        JScrollPane scrollPane = new JScrollPane(messageList);
        scrollPane.setPreferredSize(new Dimension(400, 250));

        JPanel controlPanel = new JPanel();
        statusComboBox = new JComboBox<>(new String[]{"All", "Read", "Unread"});
        statusComboBox.addActionListener(this);
        controlPanel.add(statusComboBox);

        filterTextField = new JTextField(20);
        filterTextField.addActionListener(this);
        controlPanel.add(filterTextField);

        deleteButton = new JButton("Delete");
        deleteButton.addActionListener(this);
        controlPanel.add(deleteButton);

        deleteAllButton = new JButton("Delete All");
        deleteAllButton.addActionListener(this);
        controlPanel.add(deleteAllButton);

        add(scrollPane, BorderLayout.CENTER);
        add(controlPanel, BorderLayout.SOUTH);
    }

    public void addMessage(Message message) {
        listModel.addElement(message);
    }

    public void filterMessages() {
        String status = (String) statusComboBox.getSelectedItem();
        String filterText = filterTextField.getText();
        List<Message> filteredList = new ArrayList<>();
        for (int i = 0; i < listModel.size(); i++) {
            Message message = listModel.getElementAt(i);
            if ((status.equals("All") || status.equals(message.getStatus()))
                    && (filterText.isEmpty() || message.getContent().contains(filterText))) {
                filteredList.add(message);
            }
        }
        messageList.setListData(filteredList.toArray(new Message[0]));
    }

    public void deleteSelectedMessage() {
        int index = messageList.getSelectedIndex();
        if (index >= 0) {
            listModel.remove(index);
        }
    }

    public void deleteAllMessages() {
        listModel.removeAllElements();
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == statusComboBox || e.getSource() == filterTextField) {
            filterMessages();
        } else if (e.getSource() == deleteButton) {
            deleteSelectedMessage();
        } else if (e.getSource() == deleteAllButton) {
            deleteAllMessages();
        }
    }
}

在这个类中，我们使用了 `DefaultListModel` 来存储消息列表，并将其传递给 `JList`。我们还在界面上添加了一个下拉列表框、一个文本框、一个删除选中消息的按钮和一个删除全部消息的按钮。

在 `filterMessages` 方法中，我们根据消息状态和消息内容部分匹配进行消息筛选，并将筛选结果设置为 `JList` 的数据。在 `deleteSelectedMessage` 方法中，我们删除选中的消息。在 `deleteAllMessages` 方法中，我们删除全部消息。在 `actionPerformed` 方法中，我们根据不同的事件源来调用不同的方法。

帮我补充这段代码便签管理部分的代码框架： import javax.swing.*; import java.awt.*; import java.awt.event.*; public class Memo extends JFrame { private JTextField titleField; private JTextArea contentArea; private JTextField timeField; private JButton addButton; private JButton editButton; private JButton deleteButton; private JButton viewButton; private JList memoList; private DefaultListModel listModel; public Memo() { // 初始化界面和组件 // 添加事件监听器 // 实现添加、编辑、删除和查看便签信息的功能 } public static void main(String[] args) { Memo memo = new Memo(); memo.setVisible(true); } }

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Memo extends JFrame {
private JTextField titleField;
private JTextArea contentArea;
private JTextField timeField;
private JButton addButton;
private JButton editButton;
private JButton deleteButton;
private JButton viewButton;
private JList memoList;
private DefaultListModel listModel;

public Memo() {
// 初始化界面和组件
setTitle("便签管理");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(500, 400);
setLocationRelativeTo(null);

JPanel topPanel = new JPanel(new BorderLayout());
JPanel inputPanel = new JPanel(new GridLayout(1, 3));

titleField = new JTextField();
contentArea = new JTextArea();
timeField = new JTextField();

inputPanel.add(titleField);
inputPanel.add(contentArea);
inputPanel.add(timeField);

topPanel.add(inputPanel, BorderLayout.CENTER);

JPanel buttonPanel = new JPanel(new FlowLayout());

addButton = new JButton("添加");
editButton = new JButton("编辑");
deleteButton = new JButton("删除");
viewButton = new JButton("查看");

buttonPanel.add(addButton);
buttonPanel.add(editButton);
buttonPanel.add(deleteButton);
buttonPanel.add(viewButton);

topPanel.add(buttonPanel, BorderLayout.SOUTH);

add(topPanel, BorderLayout.NORTH);

listModel = new DefaultListModel();
memoList = new JList(listModel);
JScrollPane scrollPane = new JScrollPane(memoList);

add(scrollPane, BorderLayout.CENTER);

// 添加事件监听器
addButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// 添加便签信息
String title = titleField.getText();
String content = contentArea.getText();
String time = timeField.getText();

MemoData memo = new MemoData(title, content, time);
listModel.addElement(memo);
}
});

editButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// 编辑便签信息
int index = memoList.getSelectedIndex();
if (index != -1) {
String title = titleField.getText();
String content = contentArea.getText();
String time = timeField.getText();

MemoData memo = new MemoData(title, content, time);
listModel.remove(index);
listModel.add(index, memo);
}
}
});

deleteButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// 删除便签信息
int index = memoList.getSelectedIndex();
if (index != -1) {
listModel.remove(index);
}
}
});

viewButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// 查看便签信息
int index = memoList.getSelectedIndex();
if (index != -1) {
MemoData memo = (MemoData) listModel.getElementAt(index);
titleField.setText(memo.getTitle());
contentArea.setText(memo.getContent());
timeField.setText(memo.getTime());
}
}
});
}

public static void main(String[] args) {
Memo memo = new Memo();
memo.setVisible(true);
}
}

class MemoData {
private String title;
private String content;
private String time;

public MemoData(String title, String content, String time) {
this.title = title;
this.content = content;
this.time = time;
}

public String getTitle() {
return title;
}

public String getContent() {
return content;
}

public String getTime() {
return time;
}

@Override
public String toString() {
return title + " - " + time;
}
}