public class juxing {

//编写一个矩形类，将长与宽作为矩形类的属性，在构造方法中将长、宽初始化，定义一个成员方法求此矩形面积

    int chang;

    int kuan;

    int mianji;

    double s;

    double c;

    int n = 4;

    String tuxing = "矩形";

    void xingzhuang(){  //无返回无参数

        tuxing = "矩形";

    }

   void djx(double m){     //无返回值，有参数  ？？？？

        m = c-2;

       System.out.println("对角线 = " + m);

    }

    double mianji(int chang,int kuan){  //有返回值，有参数

        return mianji= chang*kuan;

    }

    boolean bianshu(){        //有返回值，无参数

        boolean b = true;

        if (n == 4){

            System.out.println("有四条边 " + b);

        }else{

            System.out.println("不是四边形");

        }

        return b;

    }

        public static void main (String[] args){

            juxing jx = new juxing();

        jx.chang = 10;

        jx.kuan = 5;

        jx.s = jx.chang*jx.kuan;

        jx.mianji = jx.chang * jx.kuan;

        jx.c = 2 * (jx.chang + jx.kuan);

        jx.djx(jx.c);

        System.out.println("图形："+jx.tuxing);

        System.out.println("面积= "+jx.s);

        System.out.println("矩形的面积= "+jx.mianji);

        System.out.println("周长 = "+jx.c);

        //System.out.println("对角线 = "+jx.m);

        if (jx.bianshu()){

            System.out.println("这个图形是四边形");

        }else{

            System.out.println("这个图形不是四边形");

        }

    }

}