package shape;public class Shape {    //定义成员变量    private double zhouchang;    private double mianji;    public double getZhouchang() {        return zhouchang;    }    public void setZhouchang(double zhouchang) {        this.zhouchang = zhouchang;    }    public double getMianji() {        return mianji;    }    public void setMianji(double mianji) {        this.mianji = mianji;    }        }

package shape;public class Sanjiao extends Shape{    //定义新的成员方法用来求周长    public String qiuZC(double bian1,double bian2,double bian3)    {        if((bian1+bian2)>bian3&&(bian2+bian3)>bian1&&(bian1+bian3)>bian2)            return "三角形的周长为："+(bian1+bian2+bian3);        else            return "该三角形的边长不合法，两边之和必须大于第三边";                    }    }

package shape;public class Jvxing extends Shape{    //定义新的成员方法用来求周长    public String qiuZC(double chang, double kuan)    {        if(chang>0&&kuan>0)            return "矩形的周长为："+2*(chang+kuan);        else            return "该矩形的长和宽不合法，长和宽必须大于0";                }}

package shape;public class E {    public static void main(String[] args) {                //实例化三角形对象        Sanjiao sj = new Sanjiao();        System.out.println(sj.qiuZC(5, 5.6, 8));        System.out.println(sj.qiuZC(5, 5.6, 25.2));                        //实例化矩形对象        Jvxing jx= new Jvxing();        System.out.println(jx.qiuZC(5, 5.6));        System.out.println(jx.qiuZC(28, 0));    }}