说明：  Windows操作系统自带的计算器是个很方便的小工具，利用Java的GUI编程，实现一个Java GUI计算器应用程序界面，窗口标题为“计算器”，窗口布局如下图所示，在此计算器应用程序中实现“+、-、*、/”运算操作
(Calculator that comes with Windows operating system is a very handy gadget to use Java, GUI programming, a Java GUI calculator application program interface, the window titled " calculator" , the window layout as shown in this calculator applications to achieve " +,-,*,/" computing operations)