class lader{
double above,bottom,height;
lader(double a,double b,double h)
{
	above=a;
	bottom=b;
	height=h;
}
public void setAbove(double a){
	above=a;
}
void setBottom(double b){
	bottom=b;
}
private void setHeight(double h){
	height=h;
}
double computeArea(){
	return (above+bottom)*height/2.0;
}
}



public class example3
{
public static void main(String args[]){
	double area1,area2=0;
	lader laderone,ladertwo;
	laderone=new lader(5,10,12);
	ladertwo=new lader(10,20.45,20);
	area1=laderone.computeArea();
	area2=ladertwo.computeArea();
	System.out.printf("laderone和ladertwo的面積分別是：%n%f,%f\n",area1,area2);
	laderone.setAbove(10);
	ladertwo.setBottom(40);
	area1=laderone.computeArea();
	area2=ladertwo.computeArea();
	System.out.printf("laderone和ladertwo的面積分別是：%n%f,%f\n",area1,area2);
	System.out.printf("%n%f",laderone.above);
}
}