frist.java

清华大学的java教程

/*public abstract class Shape
{
	private double x,y;
    public void point()
    {
    	x = 0;
        y = 0;
    }
	abstract float area(); 
	abstract float circumference(); 
}*/

class Circle extends Shape
{ 
    public int r; 
    Circle(int r)  {this.r=r;} 
    public double area() { return 3.14*r*r; }
    public double circumference() { return 2*3.14*r; }
}
class Rectangle extends Shape
{
	public double width,height; 
    Rectangle (double w, double h) { width=w; height=h;}
    public double area()  { return width*height; }
    public double circumference() { return 2*(width+height); }
}

public class frist
{
   public static void main( String args[] )
   {
   	  double area_total=0;
   	  
      Circle c1 = new Circle(3); 
      Circle c2 = new Circle(4); 
      Circle c3 = new Circle(5); 
      Rectangle r1 = new Rectangle(3.0,4.0);
      Rectangle r2 = new Rectangle(5.0,6.0);
      Rectangle r3 = new Rectangle(7.0,8.0);
       
      Object sh[]=new Object[6];
      sh[0]=c1;
      sh[1]=c2;
      sh[2]=c3;
      sh[3]=r1;
      sh[4]=r2;
      sh[5]=r3;
      
      for(int i=0;i<6;i++)
      {
         area_total+=((Shape)sh[i]).area();
      }
       
      System.out.println("The total of area is "+area_total+"\n");
    }
}