请完成一个五子棋的java代码

以下是一个简单的五子棋 Java 代码，使用了 Swing 图形库实现了 GUI 界面：

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

public class Gobang extends JFrame {

    private static final long serialVersionUID = 1L;
    private int ROWS = 15;
    private int COLS = 15;
    private int CELL_SIZE = 30;
    private int[][] board = new int[ROWS][COLS];
    private boolean isBlack = true;

    public static void main(String[] args) {
        Gobang game = new Gobang();
        game.init();
    }

    public void init() {
        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());
        GobangBoard boardPanel = new GobangBoard();
        mainPanel.add(boardPanel, BorderLayout.CENTER);
        this.setContentPane(mainPanel);
        this.setTitle("五子棋");
        this.setSize(ROWS * CELL_SIZE, COLS * CELL_SIZE);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }

    class GobangBoard extends JPanel {

        private static final long serialVersionUID = 1L;

        public GobangBoard() {
            addMouseListener(new GobangListener());
        }

        public void paint(Graphics g) {
            g.setColor(Color.WHITE);
            g.fillRect(0, 0, ROWS * CELL_SIZE, COLS * CELL_SIZE);
            g.setColor(Color.BLACK);

            for (int i = 0; i < ROWS; i++) {
                g.drawLine(0, i * CELL_SIZE, ROWS * CELL_SIZE, i * CELL_SIZE);
            }

            for (int i = 0; i < COLS; i++) {
                g.drawLine(i * CELL_SIZE, 0, i * CELL_SIZE, COLS * CELL_SIZE);
            }

            for (int i = 0; i < ROWS; i++) {
                for (int j = 0; j < COLS; j++) {
                    if (board[i][j] == 1) {
                        g.setColor(Color.BLACK);
                        g.fillOval(i * CELL_SIZE + 2, j * CELL_SIZE + 2, CELL_SIZE - 4, CELL_SIZE - 4);
                    } else if (board[i][j] == 2) {
                        g.setColor(Color.WHITE);
                        g.fillOval(i * CELL_SIZE + 2, j * CELL_SIZE + 2, CELL_SIZE - 4, CELL_SIZE - 4);
                    }
                }
            }
        }

        class GobangListener extends MouseAdapter {
            public void mouseClicked(MouseEvent e) {
                int x = e.getX() / CELL_SIZE;
                int y = e.getY() / CELL_SIZE;

                if (x < 0 || x >= ROWS || y < 0 || y >= COLS) {
                    return;
                }

                if (board[x][y] != 0) {
                    return;
                }

                board[x][y] = isBlack ? 1 : 2;
                isBlack = !isBlack;

                repaint();
            }
        }
    }
}

这个程序包含一个 `Gobang` 类和一个 `GobangBoard` 类。`Gobang` 类负责初始化界面，包括设置标题、大小、关闭操作等；`GobangBoard` 类继承自 `JPanel`，负责绘制棋盘和处理用户的鼠标事件。在 `GobangBoard` 类中，`paint` 方法用于绘制棋盘和棋子，`GobangListener` 类用于处理用户的鼠标点击事件。