Problem Set 5

  This problem consists of 3 small parts. In the first part, you need to provide a java application, then in the second part you must write a java applet, and, finally, at the third part you need to provide, in one file, a class which can be executed both as an applet and as an application.

  For all 3 parts you need to provide a class for Point objects named MyPoint. The data members of the class should be the following:

• two doubles, named x and y, to store the x and y coordinates of the point.
• one static int, named numberMyPoints to keep truck of the number of points that have been created

  The class should be called MyPoint and should be provided in a file MyPoint.java. It should have two constructors:

• a non-argument constructor which should install zero values to both x and y
• a constructor which has two double as arguments by the names x and y.

  The constructors should take care of increasing accordingly the number of MyPoint objects that are created using the static member data numberMyPoints.

  The class should also provide a toString method which should return a string consisting of the string "(x,y) =" and the values of x and y enclosed in parentheses and separated with a comma e.g.:  (x,y) = (-4.6 , 9.5)

  Finally, the class MyPoint should have a member function named move which have two parameters named dx and dy of type double. The function move() should add the dx and dy to the values of the member data x and y, respectively.
 

Part A:

      In this part you need to provide an application, i.e. which can be executed from a console (e.g. an xterm), in a file named ps5_1a.java. The main function should print out the number of the MyPoint objects (which initially should be set to zero, since no objects would have been created).

     Then, it should create (using new) an object named p1 using the non-argument constructor (which gives zero values). Then, the number of MyPoint objects should be printed again out, using the corresponding static variable. The p1 object should also be printed out making use of the toString() function.

     Then,  MyPoint object, named p2, should be created and given the values -4.6 and 9.5, for x and the y, respectively, using the other constructor. Then, the number of MyPoint objects should be printed, again, out followed by the printing of the object p2 making use of the toString() function.

    Finally, move the point p1 by dx=4.5 and dy=0.7, using the member function move() of the class MyPoint.

The execution of the program should have an output similar to the following:

 > java ps5_1a
 

 Number of MyPoint objects = 0

 Number of MyPoint objects = 1

 p1: (x,y) = (0.0 , 0.0)

 Number of MyPoint objects = 2

 p2 = (x,y) = (-4.6 , 9.5)

 p1: (x,y) = (4.5 , 0.7)
 
 

Part B:

      In this part you need to provide an applet, i.e. which can be executed from a browser or using appletviewer, in a file named ps5_1b.java.

      The applet should use the class MyPoint to define two objects, as above, p1 and p2 with the same values as above and using the same constructors. Create a point p1 using the non-argument constructor and then move it as above by 4.5 and 0.7. Instead of printing to a console (xterm) it should paint to the browser, or to the appletviewer, the number of the MyPoint objects that have been created and the two objects, using the toString() member function.

     The resulting image of the browser or appletviewer loading the applet ps5_1b should look like below:
 
 

Number of MyPoint objects = 2       p1: (x,y) = (4.5 , 0.7)     p2 = (x,y) = (-4.6 , 9.5)

     To be able to load the applet you need to write an html file, named ps5_1b.html, which should also be submitted for grading.
 

Part C:

      In this part you need to provide in a file named ps5_1c.java a class that can be called from the console (i.e. run as an application), or from a browser (i.e. run as an applet). If it is executed as an application should give an output similar to the one provided to part A. Otherwise, if it is loaded as an applet it should result to an image similar to the one given in part B.

Note:

  Overall, for all 3 parts, you need to submit the files ps5_1a.java, ps5_1b.java, and ps5_1c.java for parts A, B and C, respectively. You also need to submit the file MyPoint.java in which the class MyPoint should be defined. Finally, you need to submit the html files ps5_1b.html and ps5_1c.html for parts B and C.

   Please, also, submit screendumps of the execution of each part, the output of parts A and C and screendump of the appletviewer (or browser) for parts B and C.

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    For this problem you need to provide five classes, Shape, Sphere, Triangle, Tetrahedron, and Point, in the files Shape.java, Sphere.java, Triangle.java, Tetrahedron.java, and Point.java, respectively.

    The provided classes should be able to support the provided in the file ps5_2.java application. This application should be able to read a number of shapes and use an array of references to Shape objects. The shapes can be spheres, triangles, tetrahedrons and their characteristics should be stored in the corresponding (Sphere, Triangle, and Tetrahedron, respectively) classes which are subclasses of the Shape class. You should not make any changes to the provided ps5_2.java file, which has the main() function and the other provided functions.

    The shapes are read and then stored in an array of references to Shape objects. Then, all shapes are printed out using polymorphism. Finally, the references to shape objects are set to null and the System.runFinalization() and the System.gc() are called to force the finalizing of the objects and  the garbage collector to run, respectively.

The hierarchy to be used is shown on the following figure:

     You need to provide each of the above classes, namely Shape, Sphere, Triangle, and Tetrahedron, in the files Shape.java, Sphere.java, Triangle.java, and Tetrahedron.java, respectively. You also need to provide the class Point, which is used by the above classes, in the file Point.java. You should figure out from the file ps5_2.java what member functions are required in order to be able to compile and run the completed program.

     Several constructors, static and non-static member functions, and finalizers are required.  All member data that are not explicitly specified, e.g. when a non-argument constructor is called, should be set to zero. The constructors should increase the static variable which counts the number of instances of that class. The finalize methods should decrease those numbers whenever an object is finalized.  Finally, all classes should have a toString() method, that can be used to print the object using the print() method of the System class.

In particular you need to provide:

1. The abstract class Shape in the file Shape.java: This class should have the following private members:

• int shapeId: to store the ID of the shape
• int numberShapes: which should be static and initialized to 0, to store the number of Shape objects. The constructor(s) should  increase the numberShapes accordingly.

2. The class Sphere in the file Sphere.java: This class should have  the following private members:

• double radius: to store the radius of the sphere
• Point center: to store the center of the sphere
• int numberSpheres, : which should be static and initialized to 0, to store the number of Sphere objects

3. The class Triangle in the file Triangle.java: This class should have  the following private members:

• Point a: to store vertex a
• Point b: to store vertex b
• Point c: to store vertex c
• int numberTriangles, : which should be static and initialized to 0, to store the number of Triangle objects

4. The class Tetrahedron in the file Tetrahedron.java: This class should have  the following private members:

• Point a: to store vertex a
• Point b: to store vertex b
• Point c: to store vertex c
• Point d: to store vertex d
• int numberTetrahedrons, : which should be static and initialized to 0, to store the number of Tetrahedron objects

 

4. The class Point in the file Point.java: This class should have  the following private members:

• double x: to store the x coordinate of the point
• double y: to store the y coordinate of the point

The main() and some other functions are provided in the file ps5_2.java:

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();
        }
}
 

The output from your program should look like the following:

  Reading the shapes...
 Printing the shapes...
 Number of shapes: 8

   Number of Spheres: 4
   Number of Triangles: 2
   Number of Tetrahedrons: 2

Shapes [ 1 ]:   Sphere
 Shape:   ID = 11
         Radius = 0.25
         Center: (x,y) = (-6.8 , 5.3)

Shapes [ 2 ]:   Triangle
 Shape:   ID = 33
         Vertex a: (x,y) = (4.1 , 5.7)
         Vertex b: (x,y) = (-3.6 , -1.2)
         Vertex c: (x,y) = (2.3 , -8.2)

Shapes [ 3 ]:   Sphere
 Shape:   ID = 101
         Radius = 0.0
         Center: (x,y) = (0 , 0)

Shapes [ 4 ]:   Triangle
 Shape:   ID = 0
         Vertex a: (x,y) = (0 , 0)
         Vertex b: (x,y) = (0 , 0)
         Vertex c: (x,y) = (0 , 0)

Shapes [ 5 ]:   Tetrahedron
 Shape:   ID = 44
         Vertex a: (x,y) = (-9.5 , 3.1)
         Vertex b: (x,y) = (-5.2 , 4.2)
         Vertex c: (x,y) = (-6.2 , 9.5)
         Vertex d: (x,y) = (-6.2 , 9.5)

Shapes [ 6 ]:   Sphere
 Shape:   ID = 147
         Radius = 0.0
         Center: (x,y) = (0 , 0)

Shapes [ 7 ]:   Tetrahedron
 Shape:   ID = 67
         Vertex a: (x,y) = (4.1 , 5.7)
         Vertex b: (x,y) = (2.3 , -8.2)
         Vertex c: (x,y) = (-9.6 , -13.6)
         Vertex d: (x,y) = (-6.2 , 9.5)

Shapes [ 8 ]:   Sphere
 Shape:   ID = 0
         Radius = 0.0
         Center: (x,y) = (0 , 0)

 Cleaning-up the shapes...

 References to shape objects are set to null

Setting shape [ 1 ]: to null
Setting shape [ 2 ]: to null
Setting shape [ 3 ]: to null
Setting shape [ 4 ]: to null
Setting shape [ 5 ]: to null
Setting shape [ 6 ]: to null
Setting shape [ 7 ]: to null
Setting shape [ 8 ]: to null

 Finalizing objects

 Running the Garbage Collector

    In Sphere finalize
                 In Shape finalize

    In Triangle finalize
                 In Shape finalize

    In Sphere finalize
                 In Shape finalize

    In Triangle finalize
                 In Shape finalize

    In Tetrahedron finalize
                 In Shape finalize

    In Sphere finalize
                 In Shape finalize

    In Tetrahedron finalize
                 In Shape finalize

    In Sphere finalize
                 In Shape finalize
 

Note:

You must submit, both electronically and in a hardcopy form, the files files Shape.java, Sphere.java, Triangle.java, Tetrahedron.java, and Point.java, in which you should provide the corresponding classes as explained above. You also need to submit the provided fileps5_2.java to facilitate the compilation and running of your program during grading. Please, submit a printout of the output from the completed program.

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  In this problem you must write a Java applet that reads a number of rectangles and determines their total area and their centroid. The source code for the applet should be provided in the file ps5_3.java as a class ps5_3.
The source code for the class Rectangle should be provided in the file Rectangle.java.

   Class Rectangle should have 3 private members:

• the center of the rectangle, which should be a point. You may use the same class that you have already developed for the class Point for the previous problems.
• the width and the height of the rectangle, which should be doubles

   The applet ps5_3 should have an array of Rectangles of size 10. The following 4 rectangles should be created and referred from the array of rectangles. For simplicity assume that all rectangles are parallel to the x and y axes.
 

Rectangle	Xc	Yc	Width	Height
1	75	130	40	30
2	100	75	30	25
3	165	155	45	45
4	195	85	30	50

   Then, the applet should draw each rectangle. The total area of rectangles and their centroid should be computed and printed out using  two decimal points only. You also need to write the number of the rectangle, R1 for rectangle, R2 for rectangle 2, and so on. Also a circle of diameter 4 should be drawn at the centroid. The following figure shows how your applet should appear:

   The centroid of a set of shapes is computed as the sum of the products of the area of each shape times its centroid coordinate (X_ci and Y_ci) divided by the total area of the cross-section. For example, the centroid (X_c,Y_c) of the following section is defined by the following formulas:

    You need to submit all files necessary to compile and run your applet, i.e. ps5_3.java, Rectangle.java, and ps5_3.html. You also need to submit a screendump of  your  applet.

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