基于Java的画图程序源代码，定义图案类型，记录鼠标拖动的起始点和终点、增加鼠标事件、鼠标释放事件、重绘屏幕、根据shape值绘制图形(Java-based drawing program source code, define the pattern type, record the starting point and end point of the mouse drag, add mouse events, mouse rele