class Lader{

 double above,bottom,height;

 Lader(){}

 Lader(double a,double b,double h){

  above=a;

  bottom=b;

  height=h;

  }

  public void setAbove(double a){

   above=a;

   }

   public void setBottom(double b){

    bottom=b;

    }

    public void setHeight(double h){

     height=h;

     }

     double Area(){

      return (above+bottom)*height/2.0;

      }

 }

 public class Example4_3{

  public static void main(String[] args){

   double area1=0,area2=0;

   Lader laderOne,laderTwo;

   laderOne =new Lader();

   laderTwo =new Lader(1,2,3);

   laderOne.setAbove(11);

   laderOne.setBottom(22);

   laderOne.setHeight(33);

   area1=laderOne.Area();

   area2=laderTwo.Area();

   System.out.println("laderOne的above,bottom和height："+laderOne.above+","+laderOne.bottom+","+laderOne.height);

   System.out.println("laderOne的面积："+area1);

   System.out.println("laderTwo的above,bottom和height："+laderTwo.above+","+laderTwo.bottom+","+laderTwo.height);

   System.out.println("laderTwo的面积："+area2);

   }

  }

 

经过一系列的查找，终于把错误全找没了。。。。。。。。。。。。。。。。。