(1)　　设计一个程序，用于根据用户输入的命令行参数数量来计算长方形、正方形、三角形的面积。如果输入的参数为一个、二个、三个则它们应分别对应正方形、长方形、三角形，如果没有参数，则通过异常处理方法现实错误消息。（用于计算面积的方法是一个重载的方法。提示：定义一个抽象的父类，并提供一个抽象的方法area(). 再派生出三个子类，重写area()方法，然后在main方法中用多态来实现具体的面积函数的调用）。-(1) design a program for user input in accordance with the command-line parameters to calculate the number of rectangular, square, triangle area. If you enter the parameters for one, two, three, respectively, they should correspond to a square, rectangle, triangle, if there is no parameter by abnormal way to deal with the reality error message. (The method used to calculate the area is an overloaded method. NOTE: the definition of an abstract parent class, and provide an abstract method area (). Send another give birth to three sub-categories, rewriting area () method, and then in the main polymorphic methods used to achieve a specific area of function calls).