testshapes.java

Beginning Java 2, SDK 1.4 Edition Exercise Code samples for this book

// Chapter 6 Exercise 1

public class TestShapes {
  public static void main(String args[]) {
    Shape[] shapes = new Shape[10];	     // Define an array of shapes.
    Point[] pts = null;                  // Stores a reference to an array of points.
    Point pt1 = null;                    // First working Point store.
    Point pt2 = null;			               // Second working Point store.
    double minRadius = 2.0;		           // Minimum radius of a circle.
    double maxRadius = 20.0;		         // Maximum radius of a circle.
    double maxDist = 100.0;		           // Maximum x,y coordinate value.
    int minPts = 2;			                 // Minimum number of points in PolyLines.
    int maxPts = 15;                     // Maximum number of points in PolyLines.
    int choice;                          // Selector for shape type.

    for(int i=0;i<shapes.length;i++) {					 
      // Generate one of four random shapes:
      choice = (int)(4.0*Math.random()); 	// Shape choice 0 to 3.

      // Coordinates are cast to int just to remove the frctional part and make the output less messy.
      // The compiler will arrange to cast the integer arguments back to double.
      switch(choice) {
        case 0:				 	// Generate a Line:
          // Generate two random points:
          pt1 = new Point((int)(Math.random()*maxDist),(int)(Math.random()*maxDist));	
          pt2 = new Point((int)(Math.random()*maxDist),(int)(Math.random()*maxDist));
          shapes[i] = new Line(pt1,pt2); 	// Add Line to Shape array.
          break;

        case 1:					// Generate a Circle:
          pt1 = new Point((int)(Math.random()*maxDist),(int)(Math.random()*maxDist));	
          shapes[i] = new Circle(pt1, (int)(minRadius+(maxRadius-minRadius)*Math.random()));
          break;

        case 2:					// Generate a Rectangle:
          // Generate two random points:
          pt1 = new Point((int)(Math.random()*maxDist),(int)(Math.random()*maxDist));	
          pt2 = new Point((int)(Math.random()*maxDist),(int)(Math.random()*maxDist));
          shapes[i] = new Rectangle(pt1,pt2);	// Add Rectangle to Shape array.
          break;

        case 3:					// Generate a PolyLine:
          // Create a Point array with a random number of elements:
          pts = new Point[minPts+(int)((maxPts-minPts)*Math.random())];

          // Fill array with random points:
          for(int j=0;j<pts.length;j++)
            pts[j] = new Point((int)(Math.random()*maxDist),(int)(Math.random()*maxDist));

          shapes[i] = new PolyLine(pts);	// Add PolyLine to Shape array.
          break;

        default:                               // We should never get to here.
          System.out.println("\nInvalid shape choice = "+choice);
          System.exit(1);
          break;
      }
    }

    // Output all the shapes in the Shape array:
    for(int i=0;i<shapes.length;i++)
      shapes[i].show();
  }
}