Computing Science 331 –
Spring 2017
Midterm Test
Name:
________________________________
Instructor:
Time allowed: 85 minutes
Marks available: 57
1.
Answer
the following short questions.
a) Member functions can (usually)
directly access the data members of an object.
Why can’t the main method? (2
marks)
b)
How is it possible for an object to have data members that its member
function cannot access directly? (2
marks)
c)
Some (Java?) programmers would argue that it is easier to code polymorphic
behaviour in Java than in C++. What
reason(s) would they give to “prove” their point? (2 marks)
d) What output does the
following program produce? Explain
briefly – with the aid of a sketch of the memory used for the data in this
program. (4 marks)
public class Short1 {
public static void
main(String[] args) {
String[] names =
{"Adam", "Bob", "Chuck"};
String[] newNames = names;
newNames[0] = new
String("SUE");
for (String s : names)
System.out.print(s +
" ");
System.out.println();
for (String s : newNames)
System.out.print(s +
" ");
System.out.println();
}
}
e)
What is the
effect of declaring an “instance” variable as static? (2 marks)
f) Consider the following code
(stored in the file B.java) …
class A {
private int size;
public A () {
this(1);
}
public A (int size) {
this.size = size;
System.out.println("Setting size " + size);
}
int
getSize() {
return size;
}
}
public class B extends A {
private String code;
public B () {
this(1, "aa");
}
public B (int size, String code) {
this.code = code;
System.out.println("Setting code '" + code + "'");
}
public static void main(String[] args) {
B yourB = new B();
B myB = new B(99, "nn");
}
}
What output will be produced by compiling and
running this code. (3 marks)
What one line is “obviously missing” from it? (No it’s not getCode.) (1 mark)
2. Assume the existence of the
usual Die
class:
public class Die {
private int faceValue;
public Die() {
faceValue = 1;
}
public void roll() {
faceValue = randomInt(1, 6);
}
private int randomInt( int low, int high) {
return (int) Math.floor(low + Math.random() * (high-low+1));
}
public int getFaceValue() {
return faceValue;
}
}
Your task is to write the Java class PairOfDice so that the following main
method will compile and run. Note that
you will need to write 4 methods. (12 marks)
public
static void main(String[] args) {
PairOfDice myDice = new
PairOfDice();
myDice.roll();
System.out.println("I
have rolled " + myDice);
System.out.println("That's
a " + myDice.getTotal());
}
Note that if this main method is executed it should
produce output of the following form:
I have rolled
2 and 5
That’s a 7
public class
PairOfDice {
3. Yes I know you were
expecting Monopoly but … a chess board consists of 64 squares (eight rows and
eight columns) arranged in two alternating colors (light and dark). The board is always placed so that the
rightmost square on the row nearest each player is a "white" square. The columns (called files)
are labelled by the letters a to h from left to right from the white player's
point of view, and the rows (called ranks)
by the numbers 1 to 8, with 1 being closest to the white player.
Each player starts the game with 16 pieces placed on
the board: 8 pawns, 2 rooks, 2 knights, 2 bishops, and a king and queen. Each piece has its own rules for moving on
the board.
Black Player’s Side
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White Player’s Side
a)
Sketch a
class diagram for this problem – showing the “obvious” 3 or 4 classes. Show associations and some multiplicity. (5 marks)
b)
Write Java
declarations for the class Square and the class Piece with the data and
behaviour you have described in part (a). (3 + 3 marks)
4. And now finally some
Monopoly! Working from the Java code
supplied on the handout …
a)
Draw a
legible sequence diagram for the move method of the MonopolyGame class. (6
marks)
b) Does the coding of the move method in part (a) more
represent distributed control or centralized control? Explain briefly. (2 marks)
c) Why might a Player object
have the Board as an instance variable? (2
marks)
d)
Write the
Java code for class Player – at least everything that is known about it from the
given code. (8 marks)
public class Player {