JavaSwing写的投球小游戏，完美模拟抛物线！双缓冲解决闪烁，提高游戏体验。所有代码纯手打，每一句都有注释。-JavaSwing write pitching game, perfect simulation parabola! Double buffering fixes flicker, improve the game experience. All code pure hand to play, each one has a comment.