1.124J Foundations of Software Engineering

Problem Set 5 - Solution

Due Date: Tuesday 10/24/00
 
The solution source code files are available in the 1.124 directory from where you can check them out using CVS. Please read and try to understand the solutions.

The solution source code files are in the source code repository directory /mit/1.124/src from where you can check them out to your directory using CVS.

To use CVS to check out any provided material from the 1.124 repository you first need to set the environment variable CVSROOT as below: (you can also put it in your .environment dotfile to avoid repetition)

% setenv CVSROOT /afs/athena.mit.edu/course/1/1.124/src

Then you can use either of the commands:

%  cvs co Problems/SOL5

% cvs co OOP_SOL5
(alias defined in 1.124/src/CVSROOT/modules)

Problem 1:[30%]

The provided solution uses AWT Applet. However, use of Swing JApplet is also an option, probably a better one that someone could have used.

MyPoint.java

class MyPoint
{
   double x;
   double y;
   static int numberMyPoints=0;

   MyPoint()
     {
       x = 0.0 ;
       y = 0.0 ;
       numberMyPoints++;
     }

   MyPoint(double x, double y)
     {
       this.x = x;
       this.y = y ;
       numberMyPoints++;
     }

    void move(double dx, double dy)
     {
       x += dx;
       y += dy ;
     }

   public String toString()
      {
        return ("(x,y) = (" + x + " , " + y + ")");
      }
}
 
 

ps5_1a.java

class ps5_1a
{
   static MyPoint p1, p2;

   public static void main(String args[])
        {
           System.out.println("\n Number of MyPoint objects = "
         + MyPoint.numberMyPoints);
           p1 = new MyPoint();
           System.out.println("\n Number of MyPoint objects = "
         +MyPoint.numberMyPoints);
     System.out.println("\n p1: " + p1);

           p2 = new MyPoint(-4.6,9.5);
           System.out.println("\n Number of MyPoint objects = "
         + MyPoint.numberMyPoints);
           System.out.println("\n p2 = " + p2);

     p1.move(4.5, 0.7);
     System.out.println("\n p1: " + p1);
        }
}
 
 

ps5_1b.java

import java.applet.Applet;
import java.awt.Graphics;

public class ps5_1b extends Applet
{
   MyPoint p1, p2;

   public void init()
        {
             p1 = new MyPoint();
            p1.move(4.5, 0.7);
            p2 = new MyPoint(-4.6, 9.5);
        }

   public void paint(Graphics g)
        {
           g.drawString("Number of MyPoint objects = "
                            + MyPoint.numberMyPoints, 40,50);
           g.drawString(" p1:  " + p1 , 40, 100);
           g.drawString(" p2:  " + p2 , 40, 150);
        }
}
 
 

ps5_1b.html

<HTML>

     <HEAD>
     <TITLE> Problem set 5: problem 1c</TITLE>
     </HEAD>

     <BODY>
       <h1> Problem Set 5: Problem 1c
       <APPLET CODE="ps5_1c.class" WIDTH=300 HEIGHT=200 align=center>
       </APPLET>
     </BODY>

</HTML>
 
 

ps5_1c.java

import java.applet.Applet;
import java.awt.Graphics;

public class ps5_1c extends Applet
{
   static MyPoint p1, p2;

   public void init()
        {
            p1 = new MyPoint();
            p2 = new MyPoint(-4.6, 9.5);
            p1.move(4.5, 0.7);
        }

   public void paint(Graphics g)
        {
          g.drawString("Number of MyPoint objects = "
                          + MyPoint.numberMyPoints, 40,50);
               g.drawString(" p1:  " + p1 , 40, 100);
               g.drawString(" p2:  " + p2 , 40, 150);
        }

   public static void main(String args[])
        {
           System.out.println("\n Number of MyPoint objects = "
                                                + MyPoint.numberMyPoints);
            p1 = new MyPoint();
            System.out.println("\n Number of MyPoint objects = "
                                                    +MyPoint.numberMyPoints);
            System.out.println("\n p1: " + p1);

            p2 = new MyPoint(-4.6,9.5);
            System.out.println("\n Number of MyPoint objects = "
                                                   + MyPoint.numberMyPoints);
           System.out.println("\n p2 = " + p2);

            p1.move(4.5, 0.7);
            System.out.println("\n p1: " + p1);
        }
}
 
 

ps5_1c.html

<HTML>

     <HEAD>
     <TITLE> Problem set 5: problem 1c</TITLE>
     </HEAD>

     <BODY>
       <h1> Problem Set 5: Problem 1c
       <APPLET CODE="ps5_1c.class" WIDTH=300 HEIGHT=200 align=center>
       </APPLET>
     </BODY>

</HTML>

Problem 2:[35%]

ps5_2.java

class ps5_2
{
   static final int SIZE = 100;
   static Shape shapes[];
 

   public static void main(String args[])
        {
           System.out.print("\n Reading the shapes...");
           readShapes();

           System.out.print("\n Printing the shapes...");
           printShapes();

           System.out.print("\n Cleaning-up the shapes...");
           cleanUpShapes();
        }
 

   static void readShapes()
        {
           shapes = new Shape[SIZE];
           Point p1,p2,p3,p4,p5,p6,p7, p8;

     p1 = new Point(4.1,5.7);
     p2 = new Point(-3.6,-1.2);
     p3 = new Point(2.3,-8.2);
     p4 = new Point(-9.5,3.1);
     p5 = new Point(-5.2,4.2);
     p6 = new Point(-6.2,9.5);
     p7 = new Point(-11.6,8.6);
     p8 = new Point(-9.6, -13.6);

           shapes[Shape.getNumberShapes()] = new Sphere(11);

           ((Sphere)shapes[0]).setRadius(0.25);
           ((Sphere)shapes[0]).setCenter(-6.8,5.3);

           shapes[Shape.getNumberShapes()] = new Triangle(33,p1,p2,p3);

           shapes[Shape.getNumberShapes()] = new Sphere(101);
           shapes[Shape.getNumberShapes()] = new Triangle();
           shapes[Shape.getNumberShapes()] = new Tetrahedron(44,p4,p5,p6,p7);
     shapes[Shape.getNumberShapes()] = new Sphere();
     shapes[Shape.getNumberShapes()-1].setID(147);
     shapes[Shape.getNumberShapes()] = new Tetrahedron();
     shapes[Shape.getNumberShapes()-1].setID(67);
     ((Tetrahedron)shapes[Shape.getNumberShapes()-1]).setVertices(p1,p3,p8,p6);
     shapes[Shape.getNumberShapes()] = new Sphere();
      }
 

   static void printShapes()
        {
            System.out.println("\n Number of shapes: " +
                              Shape.getNumberShapes());

            System.out.print("\n   Number of Spheres: " +
       Sphere.getNumberSpheres());

   System.out.print("\n   Number of Triangles: " +
                  Triangle.getNumberTriangles());
         System.out.println("\n   Number of Tetrahedrons: " +
      Tetrahedron.getNumberTetrahedrons());

            for(int i=0;i<Shape.getNumberShapes();i++)
              {
                 System.out.print("\nShapes [ " + (i+1) + " ]: "  );

                 if(shapes[i] instanceof Sphere)
                    System.out.println("  Sphere " );
                 else if(shapes[i] instanceof Triangle)
                    System.out.println("  Triangle " );
                 else if(shapes[i] instanceof Tetrahedron)
                    System.out.println("  Tetrahedron " );

                 System.out.println(shapes[i]);
              }
        }

   static void cleanUpShapes()
        {
           System.out.println("\n\n References to shape objects are set to null");
           int n = Shape.getNumberShapes();

           for(int i=0;i<n;i++)
              {
                 System.out.print("\nSetting shape [ " + (i+1) + " ]: to null"  );
                 shapes[i] = null;
              }

          System.out.println("\n\n Finalizing objects");
          System.runFinalization();

          System.out.println("\n Running the Garbage Collector\n");
          System.gc();
        }
}
 


Shape.java

abstract class Shape
{
   private int shapeID;
   private static int numberShapes=0;

   /**************** Constructors ********************/

   Shape()
   {
     shapeID = 0;
  numberShapes++;
   }

   Shape(int id)
   {
     shapeID = id;
  numberShapes++;
   }

   protected void finalize() throws Throwable
           {
               System.out.println("\n\t\t In Shape finalize\n");
               numberShapes --;
               super.finalize();
           }
 

   /******************  Set methods  ***********************/

   void setID(int id)
   {
      shapeID = id;
   }
 

   /*******************  Get methods ***********************/
   double getID()
   {
     return shapeID;
   }
 

   static int getNumberShapes()
   {
     return numberShapes;
   }
 

   /*******************  toString method  ***********************/
    public String toString()
    {
      return " Shape:   ID = " + shapeID;
    }
}
 
 

Sphere.java

class Sphere extends Shape
{
   private Point center;
   private double radius;

   private static int numberSpheres=0;
 

   /**************** Constructors ********************/

   Sphere()
   {
      super();
      center = new Point();
   radius = 0.0;
      numberSpheres++;
   }

   Sphere(int id)
   {
      super(id);
      center = new Point();
   radius = 0.0;
      numberSpheres++;
   }

   Sphere(int id, double x, double y, double radius)
   {
      super(id);
      center = new Point(x,y);
   this.radius = radius;
   }

   Sphere(int id, Point p, double radius)
   {
      super(id);
      center = new Point(p);
   this.radius = radius;
   }
   protected void finalize() throws Throwable
           {
               System.out.println("\n    In Sphere finalize");
               numberSpheres --;
               super.finalize();
           }
 

 public void setRadius(double radius)
     {
    this.radius = radius;
     }

  public void setCenter(double x, double y)
     {
      center = new Point(x,y);
     }

   public void setCenter(Point p)
     {
      center = new Point(p);
     }

   static int getNumberSpheres()
   {
      return numberSpheres;
   }
 
 

   /*******************  toString method  ***********************/
    public String toString()
    {
  return  super.toString()+ "\n\t Radius = " + radius +
    "\n\t Center: " + center ;
    }
}

Triangle.java

class Triangle extends Shape
{
   private Point a, b, c;

   private static int numberTriangles=0;
 

   /**************** Constructors ********************/

   Triangle()
   {
      super();
      a = new Point();
      b = new Point();
      c = new Point();
      numberTriangles++;
   }

   Triangle(int id, Point v1, Point v2, Point v3)
   {
      super(id);
   a = new Point(v1);
   b = new Point(v2);
   c = new Point(v3);
      numberTriangles++;

   }

   protected void finalize() throws Throwable
           {
               System.out.println("\n    In Triangle finalize");
               numberTriangles --;
               super.finalize();
           }
 

 public void setVertices(Point v1, Point v2, Point v3)
   {
   a = new Point(v1);
   b = new Point(v2);
   c = new Point(v3);
   }
 

   static int getNumberTriangles()
   {
      return numberTriangles;
   }
 
 

   /*******************  toString method  ***********************/
    public String toString()
    {
  return  super.toString()+ "\n\t Vertex a: " + a +
        "\n\t Vertex b: " + b + "\n\t Vertex c: " + c;
    }
}
 
 

Tetrahedron.java

class Tetrahedron extends Shape
{
   private Point a, b, c, d;

   private static int numberTetrahedrons=0;
 

   /**************** Constructors ********************/

   Tetrahedron()
   {
      super();
      a = new Point();
      b = new Point();
      c = new Point();
      c = new Point();
      numberTetrahedrons++;
   }

   Tetrahedron(int id, Point v1, Point v2, Point v3, Point v4)
   {
      super(id);
   a = new Point(v1);
   b = new Point(v2);
   c = new Point(v3);
   d = new Point(v3);
      numberTetrahedrons++;
   }

   protected void finalize() throws Throwable
           {
               System.out.println("\n    In Tetrahedron finalize");
               numberTetrahedrons --;
               super.finalize();
           }
 

 public void setVertices(Point v1, Point v2, Point v3, Point v4)
   {
   a = new Point(v1);
   b = new Point(v2);
   c = new Point(v3);
   d = new Point(v3);
   }
 

   static int getNumberTetrahedrons()
   {
      return numberTetrahedrons;
   }
 
 

   /*******************  toString method  ***********************/
    public String toString()
    {
  return  super.toString()+ "\n\t Vertex a: " + a +
             "\n\t Vertex b: " + b + "\n\t Vertex c: "
                    + c + "\n\t Vertex d: " + d;
    }
}

Point.java

class Point
{
   double x;
   double y;
   static int numberPoints=0;

   Point()
     {
       x = 0.0 ;
       y = 0.0 ;
       numberPoints++;
     }

   Point(double x, double y)
     {
       this.x = x;
       this.y = y ;
       numberPoints++;
     }

     Point(Point p)
     {
       this.x = p.x;
       this.y = p.y ;
       numberPoints++;
     }

   public double getX()
  {
    return x;
  }

 public double getY()
  {
    return y;
  }

    public void move(double dx, double dy)
     {
       x += dx;
       y += dy ;
     }

   public String toString()
      {
        return ("(x,y) = (" + x + " , " + y + ")");
      }
}
 

Problem 3:[35%]

ps5_3.java



import java.applet.Applet;
import java.awt.Graphics;
 

public class ps5_3 extends Applet
{
   Rectangle r[];

   public void init()
        {
     r = new Rectangle[10];
     Point p;

     p = new Point(75,130);
     r[Rectangle.getNumberRectangles()] = new Rectangle(p,40,30);

     p = new Point(100,75);
     r[Rectangle.getNumberRectangles()] = new Rectangle(p,30,25);

     p = new Point(165,155);
     r[Rectangle.getNumberRectangles()] = new Rectangle(p,45,45);

     p = new Point(195,85);
     r[Rectangle.getNumberRectangles()] = new Rectangle(p,30,50);
        }

   public void paint(Graphics g)
        {
       Point c = getCentroid();
       g.drawString("Total Area: " + getArea() , 50,20);
       g.drawString("Centroid: " + c, 50,40);

    for(int i=0; i<Rectangle.getNumberRectangles(); i++)
      {
       g.drawRect((int)(r[i].getXc()-r[i].getWidth()/2),
              (int)(r[i].getYc()-r[i].getHeight()/2),
             (int)(r[i].getWidth()),(int)(r[i].getHeight()));

        g.drawString("R"+(i+1),(int)(r[i].getXc()-r[i].getWidth()/4),
                (int)(r[i].getYc()+r[i].getHeight()/4));
      }
     g.fillOval((int)(c.getX()-2),(int)(c.getY()-2),4,4);
       }
 

   double getArea()
   {
    double sa=0.0;

    for(int i=0; i<Rectangle.getNumberRectangles(); i++)
           sa += r[i].area();

    return sa;
   }

   Point getCentroid()
     {
         double x, y, sx, sy, sax, say, sa;
         x = y = sx = sy = sax = say = sa = 0.0;

      for(int i=0; i<Rectangle.getNumberRectangles(); i++)
         {
            sx += r[i].getXc();
            sy += r[i].getYc();
            sa += r[i].area();
            sax += (r[i].area()*r[i].getXc());
            say += (r[i].area()*r[i].getYc());
         }
    return new Point(sax/sa,say/sa);
     }
}

Rectangle.java



class Rectangle
{
   private Point center;
   private double width, height;

   private static int numberRectangles=0;

   Rectangle(Point c, double w, double h)
   {
      center = new Point(c);
   width = w;
   height = h;
      numberRectangles++;
   }

   protected void finalize() throws Throwable
           {
               numberRectangles --;
               super.finalize();
           }

   static int getNumberRectangles()
   {
      return numberRectangles;
   }

   public double getXc()
   {
    return center.getX();
   }

   public double getYc()
   {
    return center.getY();
   }

   public double getWidth()
   {
    return width;
   }

   public double getHeight()
   {
    return height;
   }

   public double area()
   {
  return width * height;
   }

}
 
 

Point.java



// This class is used in both problems 2 and 3 of PS5
import java.text.*;

class Point
{
   double x;
   double y;
   static int numberPoints=0;

   Point()
     {
       x = 0.0 ;
       y = 0.0 ;
       numberPoints++;
     }

   Point(double x, double y)
     {
       this.x = x;
       this.y = y ;
       numberPoints++;
     }

     Point(Point p)
     {
       this.x = p.x;
       this.y = p.y ;
       numberPoints++;
     }

 public double getX()
  {
    return x;
  }

 public double getY()
  {
    return y;
  }

    public void move(double dx, double dy)
     {
       x += dx;
       y += dy ;
     }

   public String toString()
      {
     DecimalFormat df = new DecimalFormat("##0.##");
        return ("(x,y) = (" + df.format(x) +
       " , " +  df.format(y) + ")");
      }
}
 
 

ps5_3.html

<HTML>

     <HEAD>
     <TITLE> Problem set 5: problem 3</TITLE>
     </HEAD>

     <BODY>
       <h1>
       <APPLET CODE="ps5_3.class" WIDTH=300 HEIGHT=200 align=center>
       </APPLET>
     </BODY>

</HTML>
 
 
 


© 1.124J Foundations of Software Engineering
Prof. Kevin Amaratunga,1-274, kevina@mit.edu
TA: Petros Komodromos, 1-245, petros@mit.edu
TA: Eric Perkins, 1-245, edp@mit.edu