30．编写一个Shape类，具有属性：周长和面积； 定义其子类三角形和矩形，分别具有求周长的方法。 定义主类E，在其main方法中创建三角形和矩形类的对象， 并赋给Shape类的对象a、b，使用对象a、b来测试其特性。

//Shape类
package d922A;

public class Shape {
private double l,s;

public double getL() {
	return l;
}

public void setL(double l) {
	this.l = l;
}

public double getS() {
	return s;
}

public void setS(double s) {
	this.s = s;
}

}

//三角形子类
package d922A;

public class Shape {
private double l,s;

public double getL() {
	return l;
}

public void setL(double l) {
	this.l = l;
}

public double getS() {
	return s;
}

public void setS(double s) {
	this.s = s;
}

}

//矩形子类
package d922A;

public class Srect extends Shape {
private double width,height;
Srect(double w,double h)
{
width=w;
height=h;
}
public void zhouChang()
{
setL(2*(width+height));
}

}

//主类
package d922A;

public class TestShape {

public static void main(String[] args) {
	Striangle s= new Striangle(3, 4, 5);
	s.zhouChang();    //必须先调用周长函数
	Shape a=s;
	Srect j=new Srect(40, 50);
	j.zhouChang();
	Shape b=j;
	System.out.println(a.getL());
	System.out.println(b.getL());

}

}
//运行结果
12.0
180.0