CS111 Final Exam Review Problem Answers

GUI components, layout and behavior

GUI 1. Exploring LayoutManager differences

GUI 2. Understanding GUI code and behavior

Arrays and Iteration

Processing Arrays

public static void switch (int[] a, int slot1, int slot2) {
  if ((slot1 >= 0) && (slot1 < a.length) && (slot2 >= 0) && (slot2 < a.length)) {
    // valid parameters so do the switch
    int temp = a[slot1]; // create a temporary variable to hold one of the values
    a[slot1] = a[slot2]; // switch one element
    a[slot2] = temp; // switch the other element
  }
}

public static int [] copySwitch (int[] a, int slot1, int slot2) {
  int [] result = new int[a.length]; // create a new array of same length as a
  for (int i=0; i < a.length; i++) { // copy a to result
    result[i] = a[i];
  }
  if ((slot1 >= 0) && (slot1 < a.length) && (slot2 >= 0) && (slot2 < a.length)) {
    // valid parameters so do the switch
    result[slot1] = a[slot2]; // we can do this because integers are not shared
    result[slot2] = a[slot1]; // for Object arrays we would need a temporary variable
  }
  return result; // return the answer
}

Palindromes and Arrays

public static int[][] palindromeArray (int[] a)
  // declare and initialize integer arrays for two answers
  int [] ans1 = new int[2*a.length-1];
  int [] ans2 = new int[2*a.length-1];

  // fill the arrays halfway starting from the beginning
  for (int i=0; i < a.length; i++) {
    ans1[i] = a[i]; // copy of initial array
    ans2[a.length-1-i] = a[i]; // reverse of initial array
  }

  // fill the rest of the answer arrays by "mirroring"
  // the existing elements in the answers
  for (int i=a.length; i < ans1.length; i++) {
    int mirrorIndex = ans1.length-1-i;
    ans1[i] = ans1[mirrorIndex];
    ans2[i] = ans2[mirrorIndex];
  }

  // create the final answer array
  int [][] finalAnswer = {ans1,ans2};
  // an alternative way to create the finalAnswer is
  // int [][] finalAnswer = new int[][2];
  // finalAnswer[0] = ans1;
  // finalAnswer[1] = ans2;

  return finalAnswer;

}

Palindromes and Lists

Task 2

public static IntList [] palindromeListWhile (IntList L) {
  // initialize state variables
  IntList ans1 = L;
  IntList ans2 = ILO.reverse(L);
  IntList seq1 = tail(ans1);
  IntList seq2 = tail(ans2);

  while (!IL.isEmpty(seq1)) {
    // update state variables in iteration loop
    ans1 = IL.prepend(IL.head(seq1), ans1);
    ans2 = IL.prepend(IL.head(seq2), ans2);
    seq1 = IL.tail(seq1);
    seq2 = IL.tail(seq2);
  }

  // return answers in requested format
  return twoLists(ans1,ans2);
}

Objects, Object Diagrams, and Data Abstraction

Task 1 Object diagram is not available...sorry!

Task 2 Students can also be represented by an array of three integers which hold the intelligence rating, the diligence rating, and 10 times the gpa (assume gpas are calculated to 1 decimal place only).

public class Student {

  // Instance Variable -- name it anything we want
  private int [] attributes; // intelligence, diligence, 10*gpa

  // Constructor method
  public Student (int iRating, int dRating, double gpa) {
    // initialize instance variables
    attributes = new int[3];
    attributes[0] = iRating;
    attributes[1] = dRating;
    attributes[2] = (int) 10*gpa;
  }

  // Instance methods
  public int getIntelligence () {
    return attributes[0];
  }

  public int getDiligence () {
    return attributes[1];
  }

  public double getGPA () {
    return attributes[2] * 0.1; // or ((double)attributes[2])/10.0
  }

  public Point getIDRating () {
    return new Point(attributes[0],attributes[1]);
  }

  public void setIntelligence (int i) {
    attributes[0] = i;
  }

  public void setDiligence (int d) {
    attributes[1] = d;
  }

  public void setGPA (double gpa) {
    attributes[2] = (int) 10*gpa;
  }

  public void setIDRating (Point idRating) {
    attributes[0] = idRating.x;
    attributes[1] = idRating.y
  }

  public int getTotalRating () {
    return (int) 3*(attributes[0]+attributes[1]) + gpa;
  }

  public boolean isPassing () {
    return this.gpa >= 20;
  }

  public boolean isHardWorking () {
    return ((attributes[0]+attributes[1]) >= 10) &&
            (this.gpa >= (attributes[0]*4));
  }
}

Task 3 Students can also be represented by three integer instance variables which hold the sum of the intelligence and diligence ratings, the difference between the intelligence and diligence ratings (i.e. intelligence-diligence), and the total rating of the student as specified by the contract.

public class Student {

  // Instance Variables
  private int sumId, diffId, totalRating;

  // Constructor method
  public Student (int iRating, int dRating, double gpa) {
    updateVariables(iRating, dRating, gpa);
  }

  // Instance methods
  public int getIntelligence () {
    return (sumId + diffId)/2;
  }

  public int getDiligence () {
    return sumId - getIntelligence();
  }

  public double getGPA () {
    return (totalRating - 3*sumId)*0.1;
  }

  public Point getIDRating () {
    return new Point(getIntelligence(), getDiligence());
  }

  public void setIntelligence (int i) {
    updateVariables(i, getDiligence(), getGPA());
  }

  public void setDiligence (int d) {
    updateVariables(getIntelligence(), d, getGPA());
  }

  public void setGPA (double gpa) {
    totalRating = 3*sumId + (int)(10*gpa);
  }

  public void setIDRating (Point idRating) {
    updateVariables(idRating.x, idRating.y, getGPA());
  }

  public int getTotalRating () {
    return totalRating;
  }

  public boolean isPassing () {
    return getGPA() >= 2.0;
  }

  public boolean isHardWorking () {
    return (sum >= 10) &&
            (getGPA() >= (getIntelligence()*0.4));
  }

  // Auxiliary methods (still an instance method)
  // Since this method is not part of the contract, make it private.
  private void updateVariables (int iRating, int dRating, double gpa) {
    sumId = iRating + dRating;
    diffId = iRating - dRating;
    totalRating = 3*sumId + (int)(10*gpa);
  }
}