Answer Key
1.124J: Problem Set 5 - Solution
-
University:
Massachusetts Institute of Technology -
Course:
1.124J | Foundations of Software Engineering Academic year:
2020
-
Views:
287
Pages:
20
Author:
Rowan Mendoza
1.124J Foundations of Software Engineering
Problem Set 5 - Solution
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
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
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
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1.124J: Problem Set 5 - Solution
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