说明：  学习Java的过程中所做的联系的汇总 字符串的输入、字符串转化到整数、异常处理、流 最大公约数和最小公倍数 字符ASCII码的比较 一元二次方程根 求根公式 窗口类、按钮类、窗口中对象（如按钮）的布局、事件、绘图（Paint) 复选框、单选框、列表框、下拉选择框 菜单类、对话框类 绘图、绘图函数 按钮类、标签类
(learning through the process linked to the summary of the input string, the string to integer conversion, exception handling, flow and implements the common denominator ASCII characters in the comparison one yuan quadratic equation- roots formula window type, category buttons, window objects (such as buttons) layout, the incident, mapping (Paint) check box alone selects, list box, the drop-down menu selection box category, the category dialog graphics, mapping function button type, category label)