java上机作业，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。(Java on machine job, defines a rectangle named MyRectangle, with four private integer domains in the class, the xUp (yUp) of the rectangle (yUp) and the lower right corner (xDowm, yDown). In the class, a construction method with no parameters and a constructor with four int parameters are used to initialize the class object.)