例4-1和例4-2和例4-3

public class ComputerCircleArea{
 public static void main(String args[]){
  double radius;

  double area;
  radius=163.16;
  area=3.14*radius*radius;
  System.out.printf("半径是%5.3f的圆的面积:\n%5.3f\n",radius,area);
 }
}

 

class Circle{
 double radius;
 double getArea(){
   double area=3.14*radius*radius;
   return area;
  }
 }

public class Example4_2{
 public static void main(String args[]){
  Circle circle;
  circle=new Circle();
  circle.radius=163.16;
  double area=circle.getArea();
  System.out.printf("半径是%5.3f的圆的面积:\n%5.3f\n",circle.radius,area);
 }
}

 

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 computeArea(){
   return (above+bottom)*height/2.0;
  }
 }

 public class Example4_1{
    public static void main(String args[]){
     double area1=0,area2=0;
     Lader laderOne,laderTwo;
     laderOne=new Lader();
     laderTwo=new Lader(10,88,20);
     laderOne.setAbove(16);
     laderOne.setBottom(26);
     laderOne.setHeight(100);
     laderTwo.setAbove(300);
     laderTwo.setBottom(500);
     area1=laderOne.computeArea();
     area2=laderTwo.computeArea();
     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);
    }
   }