COMP-202A, Fall 2010, All Sections
FINAL EXAM SOLUTIONS



SHORT QUESTIONS
---------------


1.

a)
Correct option: Does not cause a compilation error; an object is bound to the
		call
Target object:	this / the target of the call to method second()

b)
Correct option: Causes a compilation error
Explanation:	The call causes a compilation error because an attempt is made
		to call an instance method using a class name in front of the
		dot operator. Calls to an instance method must be bound to an
		instance of the class in which the method is define, and using
		the name of the class specifies no such instance.

c)
Correct option: Causes a compilation error
Explanation:	The this reserved word represents the target of a call to an
		instance method, but a static method such as third() does not
		have a target; therefore, the use of the this reserved word is
		forbidden in a static method.

d)
Correct option:	Does not cause a compilation error; no object is bound to the
		call
Explanation:	The method being called here is third(), a static method, and
		calls to static methods are never bound to an object.


2.

The problem lies with the line
	public void SerialNumber()
which is found right after the member variable declarations of the SerialNumber
class.

The header of a constructor never specifies a return type. Therefore, the above
line is the header for a method which happens to have the same name as the
class, not the header of a constructor. As a result, this method does not get
invoked when the new operator is used to create a new object, and no explicit
constructor is declared in the SerialNumber class. This in turn causes a
constructor which takes no parameters and initializes instance variables to
default values to be provided for the class by the compiler. Considering that
this constructor is the one that is called whenever a SerialNumber object is
created, and that the default value assigned to instance variables of type int
is 0, the value stored in the number instance variable of every SerialNumber
which is created will be 0.

To fix the problem, simply remove the reserved word void from the above line, so
that it becomes:
	public SerialNumber()
This will change the method into a proper constructor, thus ensuring that the
value stored in the instance variable of every SerialNumber object is unique.


3.

add(Vector2D)
u + v == (4.0, 6.0)
add(double, double)
v + (5, 6.0) == (8.0, 10.0)
add(int, int)
u + (7, 8) == (14.0, 16.0)



LONG QUESTIONS
--------------


4.

a)
- sequence (member / instance variable)

b)
- sequence (member / instance variable)
- other (formal parameter)

c)
- sequence (local variable; the sequence member variable is shadowed by the
  sequence local variable and therefore not in scope)
- other (formal parameter)
- i (local variable)

d)
- sequence (local variable; again, the sequence member variable is shadowed by
  the sequence local variable and therefore not in scope)
- other (formal parameter)

e)
- foo (formal parameter)
- reader (local variable)


5.

1: {3, 2}
2: {2, 11}
3: {{2, 2}, {2, 11}}
4: [L: 101, R: 100, S: 106], [L: 104, R: 101, S: 106]
5: {[L: 37, R: 102, S: 106], [L: 41, R: 103, S: 106]}
6: {[L: 101, R: 104, S: 106], [L: 104, R: 101, S: 106]}



PROGRAMMING
-----------


6. 

public class Loan {
  private Subscriber borrower;
  private String callNumber;
  private Date returnDate;
  private boolean returnStatus;

  public Loan(Subscriber myBorrower, String myNumber, Date myReturnDate,
    boolean myReturnStatus) {
    this.borrower = myBorrower;
    this.callNumber = myNumber;
    this.returnDate = myReturnDate;
    this.returnStatus = myReturnStatus;
  }

  public Subscriber getBorrower() {
    return this.borrower;
  }

  public String getCallNumber() {
    return this.callNumber;
  }

  public Date getReturnDate() {
    return this.returnDate;
  }

  public boolean isReturned() {
    return this.returnStatus;
  }

  public void setReturned(boolean newStatus) {
    this.returnStatus = newStatus;
  }
}


7.

import java.util.ArrayList;

public class Subscriber {
  private String name;
  private ArrayList<Loan> loans;
  
  public Subscriber(String myName) {
    this.name = myName;
    this.loans = new ArrayList<Loan>();
  }

  public String getName() {
    return name;
  }

  public Loan findLoan(String callNumber) {
    Loan theLoan;
    Loan element;
    int i;
    int size;

    theLoan = null;
    size = this.loans.size();
    i = 0;
    while (i < size && theLoan == null) {
      element = this.loans.get(i);
      if (callNumber.equalsIgnoreCase(element.getCallNumber()) &&
	!element.isReturned()) {
        theLoan = element;
      } else {
        i = i + 1;
      }
    }
    return theLoan;
  }

  public boolean addLoan(String callNumber, Date returnDate, boolean
    returnStatus) {
    boolean result;

    result = false;
    if (findLoan(callNumber) == null) {
      this.loans.add(new Loan(this, callNumber, returnDate, returnStatus));
      result = true;
    }
    return result;
  }

  public ArrayList<Loan> getLoans() {
    return new ArrayList<Loan>(this.loans);
  }

  public ArrayList<Loan> getLoans(LoanFilter filter) {
    ArrayList<Loan> selectedLoans;
    Date returnDate;
    Loan element;
    int size;

    selectedLoans = new ArrayList<Loan>();
    size = this.loans.size();
    for (int i = 0; i < size; i++) {
      element = this.loans.get(i);
      if (filter.accept(element)) {
        selectedLoans.add(element);
      }
    }
    return selectedLoans;
  }

  public String toString() {
    String result;

    result = name + ": " + this.loans.size() + " loan";
    if (this.loans.size() > 1) {
      result = result + "s";
    }
    return result;
  }
}


8.

import java.io.File;
import java.util.Scanner;

public class SubscriberFileReader {
  public static Subscriber readSubscriberFile(String fileName)
    throws java.io.IOException {
    Subscriber subscriber;
    Scanner reader;
    String callNumber;
    Date borrowedDate;
    Date returnDate;

    reader = new Scanner(new File(fileName));
    subscriber = new Subscriber(reader.nextLine());
    while(reader.hasNext()) {
      callNumber = reader.next();
      returnDate = new Date(reader.nextInt(), reader.nextInt(),
        reader.nextInt());
      subscriber.addLoan(callNumber, returnDate, reader.nextBoolean());
    }
    reader.close();
    return subscriber;
  }
}


9.

import java.io.File;
import java.io.PrintStream;
import java.util.ArrayList;

public class ReportWriter {
  public static void generateReport(Subscriber[] subscribers, String fileName)
    throws java.io.IOException {
    PrintStream writer;    
    ArrayList<Loan> lateLoans;
    Loan element;
    Date returnDate;
    int size;
    int number;

    writer = new PrintStream(new File(fileName));
    writer.println("LIST OF LATE DOCUMENTS");
    writer.println();
    writer.println("Date: " + new Date());
    writer.println();

    number = 0;
    for (int i = 0; i < subscribers.length; i++) {
      lateLoans = subscribers[i].getLoans(LoanFilter.LATE_LOANS);
      if (lateLoans.size() > 0) {
        writer.println("- Subscriber: " + subscribers[i].getName()); 
        size = lateLoans.size();
        for (int j = 0; i < size; i++) {
          element = lateLoans.get(j);
          writer.println("\t- " +  element.getCallNumber() + " (Due: " +
            element.getReturnDate() + ")");
        }
        number = number + size;
      }
    }
    writer.println();
    writer.println("Total number of late documents: " + number);
    writer.close();
  }
}


10.

public class ReportGenerator {
  public static void main(String[] args) throws java.io.IOException {
    Subscriber[] subscribers;

    if (args.length < 1) {
      System.err.println("Usage: java ReportGenerator <outfile> [<infile>]*");
    } else {
      subscribers = new Subscriber[args.length - 1];
      for (int i = 0; i < subscribers.length; i++) {
        subscribers[i] = SubscriberFileReader.readSubscriberFile(args[i + 1]);
      }
      ReportWriter.generateReport(subscribers, args[0]);
    }
  }
}