写一个Java通讯系统。要求实现增删改查的功能

好的，下面是一个简单的Java通讯系统实现，包括增删改查的功能。这个系统使用了Java Swing来构建GUI界面，使用JDBC来连接MySQL数据库。

注意：这个示例仅用于演示Java通讯系统的实现方式，实际应用中需要根据具体的业务需求进行调整。

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Vector;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;

public class CommunicationSystem {

    private JFrame frame;
    private JTextField textFieldUsername;
    private JTextField textFieldPassword;
    private JTable table;
    private DefaultTableModel tableModel;

    private Connection conn;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    CommunicationSystem window = new CommunicationSystem();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public CommunicationSystem() {
        initialize();
        connectToDatabase();
        loadData();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        JLabel lblUsername = new JLabel("Username:");
        lblUsername.setBounds(10, 10, 80, 20);
        frame.getContentPane().add(lblUsername);

        textFieldUsername = new JTextField();
        textFieldUsername.setBounds(100, 10, 100, 20);
        frame.getContentPane().add(textFieldUsername);
        textFieldUsername.setColumns(10);

        JLabel lblPassword = new JLabel("Password:");
        lblPassword.setBounds(10, 40, 80, 20);
        frame.getContentPane().add(lblPassword);

        textFieldPassword = new JTextField();
        textFieldPassword.setBounds(100, 40, 100, 20);
        frame.getContentPane().add(textFieldPassword);
        textFieldPassword.setColumns(10);

        JButton btnAdd = new JButton("Add");
        btnAdd.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                addData();
            }
        });
        btnAdd.setBounds(220, 10, 80, 20);
        frame.getContentPane().add(btnAdd);

        JButton btnDelete = new JButton("Delete");
        btnDelete.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                deleteData();
            }
        });
        btnDelete.setBounds(220, 40, 80, 20);
        frame.getContentPane().add(btnDelete);

        JButton btnUpdate = new JButton("Update");
        btnUpdate.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                updateData();
            }
        });
        btnUpdate.setBounds(310, 10, 80, 20);
        frame.getContentPane().add(btnUpdate);

        JButton btnSearch = new JButton("Search");
        btnSearch.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                searchData();
            }
        });
        btnSearch.setBounds(310, 40, 80, 20);
        frame.getContentPane().add(btnSearch);

        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setBounds(10, 70, 414, 181);
        frame.getContentPane().add(scrollPane);

        tableModel = new DefaultTableModel();
        tableModel.addColumn("ID");
        tableModel.addColumn("Username");
        tableModel.addColumn("Password");

        table = new JTable(tableModel);
        scrollPane.setViewportView(table);
    }

    /**
     * Connect to the MySQL database.
     */
    private void connectToDatabase() {
        String url = "jdbc:mysql://localhost:3306/communication_system";
        String user = "root";
        String password = "123456";
        try {
            conn = DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * Load data from the database.
     */
    private void loadData() {
        String sql = "SELECT * FROM user";
        try {
            PreparedStatement pstmt = conn.prepareStatement(sql);
            ResultSet rs = pstmt.executeQuery();
            while (rs.next()) {
                int id = rs.getInt("id");
                String username = rs.getString("username");
                String password = rs.getString("password");
                Vector<String> rowData = new Vector<String>();
                rowData.add(Integer.toString(id));
                rowData.add(username);
                rowData.add(password);
                tableModel.addRow(rowData);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * Add data to the database.
     */
    private void addData() {
        String username = textFieldUsername.getText();
        String password = textFieldPassword.getText();
        if (username == null || username.length() == 0 || password == null || password.length() == 0) {
            JOptionPane.showMessageDialog(frame, "Username and password cannot be empty.");
            return;
        }
        String sql = "INSERT INTO user (username, password) VALUES (?, ?)";
        try {
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, username);
            pstmt.setString(2, password);
            pstmt.executeUpdate();
            Vector<String> rowData = new Vector<String>();
            rowData.add("");
            rowData.add(username);
            rowData.add(password);
            tableModel.addRow(rowData);
            JOptionPane.showMessageDialog(frame, "Add data successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(frame, "Add data failed.");
        }
    }

    /**
     * Delete data from the database.
     */
    private void deleteData() {
        int selectedRow = table.getSelectedRow();
        if (selectedRow < 0) {
            JOptionPane.showMessageDialog(frame, "Please select a row to delete.");
            return;
        }
        int id = Integer.parseInt((String) tableModel.getValueAt(selectedRow, 0));
        String sql = "DELETE FROM user WHERE id = ?";
        try {
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            pstmt.executeUpdate();
            tableModel.removeRow(selectedRow);
            JOptionPane.showMessageDialog(frame, "Delete data successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(frame, "Delete data failed.");
        }
    }

    /**
     * Update data in the database.
     */
    private void updateData() {
        int selectedRow = table.getSelectedRow();
        if (selectedRow < 0) {
            JOptionPane.showMessageDialog(frame, "Please select a row to update.");
            return;
        }
        int id = Integer.parseInt((String) tableModel.getValueAt(selectedRow, 0));
        String username = textFieldUsername.getText();
        String password = textFieldPassword.getText();
        if (username == null || username.length() == 0 || password == null || password.length() == 0) {
            JOptionPane.showMessageDialog(frame, "Username and password cannot be empty.");
            return;
        }
        String sql = "UPDATE user SET username = ?, password = ? WHERE id = ?";
        try {
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, username);
            pstmt.setString(2, password);
            pstmt.setInt(3, id);
            pstmt.executeUpdate();
            tableModel.setValueAt(username, selectedRow, 1);
            tableModel.setValueAt(password, selectedRow, 2);
            JOptionPane.showMessageDialog(frame, "Update data successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(frame, "Update data failed.");
        }
    }

    /**
     * Search data in the database.
     */
    private void searchData() {
        String username = textFieldUsername.getText();
        String sql = "SELECT * FROM user WHERE username = ?";
        try {
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, username);
            ResultSet rs = pstmt.executeQuery();
            tableModel.setRowCount(0);
            while (rs.next()) {
                int id = rs.getInt("id");
                String password = rs.getString("password");
                Vector<String> rowData = new Vector<String>();
                rowData.add(Integer.toString(id));
                rowData.add(username);
                rowData.add(password);
                tableModel.addRow(rowData);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

这个Java通讯系统使用了JDBC连接MySQL数据库，实现了增删改查的功能。在GUI界面中，用户可以输入用户名和密码，然后通过点击对应的按钮来实现增删改查的功能。这个系统还可以根据用户名来进行查询，查询结果会显示在表格中。