定义一个名为MyRectangle的矩形，类中有四个私有整型域，分别是矩形的左上角坐标（xUp，yUp）和右下角坐标（xDowm，yDown）；类中定义没有参数的构造方法和有四个int参数的构造方法，用来初始化类对象。(A rectangle named MyRectangle is defined with four private integer domains in the class, the xUp (yUp) of the rectangle, and the xDowm (yDow