THE UNIVERSITY OF AUCKLAND

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1 THE UNIVERSITY OF AUCKLAND SECOND SEMESTER, 2008 Campus: Tamaki COMPUTER SCIENCE TEST Software Design and Construction (Time allowed: 60 minutes) NOTE: Attempt ALL questions. Write your answers in the space provided. There is space at the back for answers that overflow the allotted space. No Calculators are permitted. An appendix with a simplified API is included on the last few pages. You may detach this appendix Surname Forenames Student ID Login (UPI) Question Marks Out of Question 1 15 Question 2 15 Question 3 15 Question 4 15 Total 60

2 Question 1: Inheritance & Polymorphism [15 marks] Given the following classes: class A1 { protected int x=10; public static int y=20; public A1() { x = y++; public A1(int x) { this.x = --y + x; public String tostring() { return "x=" + x + ", y=" + y; class B1 extends A1 { protected int x=100; public static int y=200; public B1() { x = y++; public String tostring() { return "super.x=" + super.x + ", super.y=" + super.y + ", x=" + x + ", y=" + y; class C1 extends A1 { public String tostring() { return super.tostring(); class D1 extends A1 { public D1() { this(40); public D1(int x) { super.x = x; public String tostring() { return super.tostring(); What will be printed after executing the following program? Write down the answer in the boxes provided. public class TestApp1 { public static void main(string[] args) { A1 p = new A1(); System.out.println(p); // 2 marks -2- CONTINUED

3 B1 q = new B1(); System.out.println(p); System.out.println(q); // 4 marks A1 r = new A1(30); System.out.println(r); // 3 marks C1 s = new C1(); System.out.println(s); // 2 marks D1 t = new D1(); System.out.println(t); // 2 marks -3- CONTINUED

4 Question 2: Inheritance [15 marks] In assignment 1, you were asked to add several changes to the program which displays moving shapes "bouncing" off the edges of the window. Create a new MovingSpecialCircle class which draws a special circle on the window. For example, the default border colour is black and the default fill colour is yellow. The transparency degree is 0.5F. An example of the special circle is given below. The centre area of the shape is a circle with the fill colour (yellow) and a transparency degree of 0.5. The background of the shape is a rectangle with the border colour (black) without any transparency degree. You set transparency by creating an AlphaComposite object then passing it to the setcomposite method of the Graphics2D object. import java.awt.*; public abstract class MovingShape { public int marginwidth, marginheight; // the margin of the animation panel area protected Point p; // the top left corner of the shapes protected int width, height; // the width and height of the shapes protected Color fillcolor; // the fill colour of the shapes protected MovingPath path; // the moving path of the shapes protected boolean selected = false; // draw handles if selected protected Color bordercolor; // the border colour of the shapes /** constructor to create a shape with default values public MovingShape() { this(0, 0, 20, 20, 500, 500, Color.blue, Color.black, 0); /** constructor to create a shape x the x-coordinate of the new shape y the y-coordinate of the new shape w the width of the new shape h the height of the new shape mw the margin width of the animation panel mh the margin height of the animation panel c the colour of the new shape typeofpath the path of the new shape public MovingShape(int x, int y, int w, int h, int mw, int mh, Color fc, Color bc, int pathtype) { p = new Point(x,y); marginwidth = mw; marginheight = mh; fillcolor = fc; bordercolor = bc; width = w; height = h; setpath (pathtype); /** abstract contains method * Returns whether the point p is inside the shape or not. p the mouse point public abstract boolean contains(point p); /** abstract draw method * draws the shape g the Graphics control public abstract void draw(graphics g); -4- CONTINUED

5 /** Returns the x-coordinate of the shape. the x coordinate public int getx() { return p.x; /** Returns the y-coordinate of the shape. the y coordinate public int gety() { return p.y; /** Returns the selected property of the shape. the selected property public boolean isselected() { return selected; /** Sets the selected property of the shape. * When the shape is selected, its handles are shown. s the selected value public void setselected(boolean s) { selected = s; /** Sets the width of the shape. w the width value public void setwidth(int w) { width = w; /** Sets the height of the shape. h the height value public void setheight(int h) { height = h; /** Draws the handles of the shape g the Graphics control public void drawhandles(graphics g) { // if the shape is selected, then draw the handles if (isselected()) { g.setcolor(color.black); g.fillrect(p.x -2, p.y-2, 4, 4); g.fillrect(p.x + width -2, p.y + height -2, 4, 4); g.fillrect(p.x -2, p.y + height -2, 4, 4); g.fillrect(p.x + width -2, p.y-2, 4, 4); /** Sets the fill colour of the shape. c the fill colour public void setfillcolor(color c) { fillcolor = c; /** Sets the border colour of the shape. c the border colour public void setbordercolor(color c) { bordercolor =c; /** moves the shape by the path public void move() { path.move(); CONTINUED

6 import java.awt.*; public class MovingRectangle extends MovingShape { /** constructor to create a rectangle with default values public MovingRectangle() { super(); /** constructor to create a rectangle shape public MovingRectangle(int x, int y, int w, int h, int mw, int mh, Color fc, Color bc, int typeofpath) { super(x,y,w,h,mw,mh,fc,bc, typeofpath); /** draws the rectangle with the fill colour * If it is selected, draws the handles g the Graphics control public void draw(graphics g) { g.setcolor(fillcolor); g.fillrect(p.x, p.y, width, height); g.setcolor(bordercolor); g.drawrect(p.x, p.y, width, height); drawhandles(g); /** Returns whether the point is in the rectangle or not true if and only if the point is in the rectangle, false otherwise. public boolean contains(point mousept) { return (p.x <= mousept.x && mousept.x <= (p.x + width + 1) && p.y <= mousept.y && mousept.y <= (p.y + height + 1)); -6- CONTINUED

7 Complete the class MovingSpecialCircle below. Do not duplicate code unnecessarily. import java.awt.*; public class MovingSpecialCircle { -7- CONTINUED

8 Question 3: Nested Classes [15 marks] Consider the program from assignment 1, a simplified version of the MovingPath is given below. import java.awt.*; public abstract class MovingShape { public int marginwidth, marginheight; // the margin of the animation panel area protected Point p; // the top left corner of the shapes protected int width, height; // the width and height of the shapes protected Color fillcolor; // the fill colour of the shapes protected MovingPath path; // the moving path of the shapes protected boolean selected = false; // draw handles if selected protected Color bordercolor;... /** moves the shape by the path public void move() { path.move(); public abstract class MovingPath { protected int deltax=2, deltay = 2; // moving distance /** constructor public MovingPath() { /** abstracts move method * moves the shape according to the path public abstract void move(); /** Sets the path of the shape. pathid the integer value of the path public void setpath() { path = new SimpleFallingPath(); public class SimpleFallingPath extends MovingPath { /** constructor to initialise values for a falling path public SimpleFallingPath() { /** moves the shape public void move() { p.y = p.y + deltay; if (p.y > marginheight) p.y = 0; You are required to modify the above program. Your task is to rewrite the SimpleFallingPath class. Rewrite it using an anonymous class. An anonymous class is a local class without a name, defined and instantiated in a single concise expression using the new operator. -8- CONTINUED

9 public abstract class MovingShape {... /** moves the shape by the path public void move() { path.move(); public abstract class MovingPath { protected int deltax=2, deltay = 2; // moving distance /** constructor public MovingPath() { /** abstracts move method * moves the shape according to the path public abstract void move(); /** Sets the shape s path. pathid the integer value of the path public void setpath() { path = -9- CONTINUED

10 Question 4: Swing [15 marks] You are required to complete a program to be used to enter a grade/mark for three different subjects: Maths, History and Science. Your program should also calculate and display the average mark. You must use an input prompt to ask for the grades and use a message dialog to display the average mark. The input prompt should be as follows: The result is shown in the picture below CONTINUED

11 import ; //(2 marks) public class Grades { public static void main(string[] args) { int mathgrade = 0; int historygrade = 0; int sciencegrade = 0; double average = 0; //enter mark/grade for Maths subject (3 marks) //enter mark/grade for History subject (3 marks) //enter mark/grade for Science subject (3 marks) // Compute average average = (mathgrade+historygrade+sciencegrade)/3; //Display result (4 marks) -11- CONTINUED

12 Overflow Sheet 1 Write the question number next to your answer. You must ALSO indicate in the allotted space that you have used the overflow sheet CONTINUED

13 Overflow Sheet 2 Write the question number next to your answer. You must ALSO indicate in the allotted space that you have used the overflow sheet CONTINUED

14 Overflow Sheet 3 Write the question number next to your answer. You must ALSO indicate in the allotted space that you have used the overflow sheet CONTINUED

15 Rough Working You may remove this page from the test script if you wish. This page will not be marked APPENDIX FOLLOWS

16 Appendix You may remove this page from the test script if you wish. This page will not be marked. java.awt class Graphics void setcolor(color) void drawline(int, int, int, int) void drawoval(int, int, int, int) void drawpolygon(int[], int[], int) void drawpolygon(polygon) void drawrect(int, int, int, int) void filloval(int, int, int, int) void fillpolygon(int[], int[], int) void fillpolygon(polygon) void fillrect(int, int, int, int) java.awt Class Graphics2D void setcomposite(composite comp) void setpaint(paint paint) void setstroke(stroke s) Stroke getstroke() Composite getcomposite() Paint getpaint() java.awt Class AlphaComposite AlphaComposite getinstance(int rule, float alpha) (rule: AlphaComposite.SRC_OVER, AlphaComposite.CLEAR...) javax.swing Class JOptionPane static void showmessagedialog(component parentcomponent, Object message) static void showmessagedialog(component parentcomponent, Object message, String title, int messagetype) static int showconfirmdialog(component parentcomponent, Object message) static int showconfirmdialog(component parentcomponent, Object message, String title, int optiontype) static String showinputdialog(component parentcomponent, Object message) static String showinputdialog(component parentcomponent, Object message, Object initialselectionvalue) static int showoptiondialog(component parentcomponent, Object message, String title, int optiontype, int messagetype, Icon icon, Object[] options, Object initialvalue)... messagetype ERROR_MESSAGE INFORMATION_MESSAGE WARNING_MESSAGE QUESTION_MESSAGE PLAIN_MESSAGE optiontype YES_NO_OPTION YES_NO_CANCEL_OPTION OK_CANCEL_OPTION... END