说明：  2.设计一个9x9的棋盘窗口，用黑白相间颜色填充棋盘。棋盘大小为600x600，标题为“棋盘”，窗口大小不可改变。程序文件命名为Exe8_2.java。
(2. Design a 9x9 board window, filling the board with black and white colors. Board size is 600x600, titled chessboard , the window size can not be changed. Program file named Exe8_2.java.)