Java Connect4游戏。我想检查列是否已满

public class Connect4Game {
    private static final int ROWS = 6;
    private static final int COLS = 7;
    private char[][] board = new char[ROWS][COLS];

    public Connect4Game() {
        // 初始化棋盘为空
        for (int i = 0; i < ROWS; i++) {
            for (int j = 0; j < COLS; j++) {
                board[i][j] = ' ';
            }
        }
    }

    public boolean isColumnFull(int col) {
        if (col < 0 || col >= COLS) {
            throw new IllegalArgumentException("Invalid column index");
        }
        // 检查该列的第一个格子是否为空
        return board[0][col] != ' ';
    }

    public static void main(String[] args) {
        Connect4Game game = new Connect4Game();
        int columnToCheck = 3;
        if (game.isColumnFull(columnToCheck)) {
            System.out.println("Column " + columnToCheck + " is full.");
        } else {
            System.out.println("Column " + columnToCheck + " is not full.");
        }
    }
}