package mytext;public class juxing {            juxing()        {                }            /*juxing(String jx)        {            String juxing = jx;                                }*/        String juxing;            double chang;            double kuan;            double mj;        double mianji(double chang,double kuan){                         return mj= chang*kuan;        }                public static void main (String[] args){                       juxing jx = new juxing();                            jx.chang = 5;                        jx.kuan = 2;                        jx.mj = jx.chang * jx.kuan;                        System.out.println("矩形的面积= "+jx.mj);                                   }                                }