package zuoye8;public abstract class Shape {		private double zhouchang ;	private double mianji ;			public Shape(double zhouchang, double mianji) {		super();		this.zhouchang = zhouchang;		this.mianji = mianji;			}	public Shape() {		super();	}	//抽象一个周长方法	 public  double zhouchang ()	 {		return zhouchang;}	 	}

package zuoye8;public class Juxing extends Shape {		private double c;	private double d;	public Juxing( double c, double d) {		super();		this.c = c;		this.d = d;			}	@Override	public double zhouchang() {		double zhouchang ;		zhouchang =(c+d)*2;		return zhouchang ;	}}

package zuoye8;public class Sanjaio extends Shape {	//三角形三边属性	private double a;	private double b;	private double c;			public Sanjaio( double a, double b, double c) {		super();		this.a = a;		this.b = b;		this.c = c;	}	public Sanjaio() {			}	//周长			 public void	 zhouchang (double a,double b,double c)	 {		 if(a+b>c&&Math.abs(a-b)<c)//绝对值，保证是正整数			{			 double zhouchang ;			 System.out.println(zhouchang =a+b+c);			 			}			else			{				System.out.println("这不是三角形");							}		 	 }		}

package zuoye8;public class E {	public static void main(String[] args) {			Juxing j=new Juxing(3,4);		System.out.println("长=4，宽=3的矩形周长="+j.zhouchang());			Sanjaio s=new Sanjaio();		System.out.println( "边分别是3,4,5的三边形周长是：");		s.zhouchang(3, 4, 5);				s.zhouchang(3,1,5);	}}