设计一矩形类Rectangular，提供计算矩形周长和面积等方法。

思考：如何定义属性和方法，可以更好地满足信息隐藏和封装的原则？对于这个类，定义几个构造函数合适？

写一测试用类，利用该矩形类，由用户输入每块土地的长与宽，程序计算其面积并显示出来。-Design a rectangle class the Rectangular, the method of calculation of the rectangular perimeter and area. Thinking: how to define properties and methods that can better meet the principle of information hiding and encapsulation? For this class, the definition of several constructors appropriate? Write a test class, use the Rectangle class, the length and width of each block of land entered by the user, the program to calculate the area and displayed.