声明一个矩形类Rectangle，其中有多个构造方法。用不同的构造方法创建对象，并输出矩形的周长和面积。

Rectangle r[] = new Rectangle[6]; r[0] = new Rectangle(); r[1] = new Rectangle(new Dimension(10,10)); r[2] = new Rectangle(10,10); r[3] = new Rectangle(10,10, 100, 2); r[4] = new Rectangle(new Point(4,5)); r[5] = new Rectangle(new Poin