(a)

F In Java, files can be opened for reading, or writing, but not both.

(b)

T Classes can have data fields that are arrays of values.

(c)

F Two dimensional arrays always have the same number of rows and columns.

(d)

T All elements of an array are of the same type.

(e)

T A Java source file can contain any number of classes with package access.

(f)

F Data fields can only be declared as private.

(g)

T System.out is a static public variable.

(h)

T Math.PI is a static public variable.

(i)

T After the following code is executed b[2] has the value 3.

     int[] a = {1, 2, 3, 4, 5};
     int[] b = a;
     a[2] = 5;

(j)

T The following code copies array a into array b, in reverse order:

    for (int i = 0; i < a.length; i++)
        b[i] = a[i];

(a)

Write code that sets up an array cheese to hold 10 strings.

String [] cheese = new String[10];

(b)

Write code that fills each element of the array cheese with the string "cheddar".

for (int i=0; i < 10; i++)
  cheese[i] = "cheddar";

(c)

Write code that opens, for reading, a text file with the name, input.dat.

TextInputStream ins = new TextInputStream("input.dat");

(d)

Write code that opens a text file with the name, output.dat, for writing, and writes "Hello, world" to the file output.dat.

TextOutputStream outs = new TextOutputStream("output.dat");
outs.println("Hello, world");

public void rosie(int n)
{
   Point oldPt = new Point(5,0);
   Point newPt;

   for (int i = 0 ; i < 100 ; i++)
   {
      double theta = i*n*Math.PI/100;
      double r = 5*Math.cos(5*theta);
      newPt = new Point(r*Math.cos(theta), r*Math.sin(theta));
      new Line(oldPt, newPt).draw();
      oldPt = newPt; 
   }
}

There is a typo in the above function. The intended function was:

public void rosie(int n)
{
   Point oldPt = new Point(5,0);
   Point newPt;

   for (int i = 0 ; i < 100 ; i++)
   {
      double theta = i*n*2*Math.PI/100;
      double r = 5*Math.cos(theta);
      newPt = new Point(r*Math.cos(theta), r*Math.sin(theta));
      new Line(oldPt, newPt).draw();
      oldPt = newPt; 
   }
}

(a)

What is the output of rosie(2)?
Output:

Output of intended function:

(b)

What is the output of rosie(5)?
Output:

Output of intended function:

LINES WRITTEN BY A BEAR OF VERY LITTLE BRAIN

On Monday, when the sun is hot

I wonder to myself a lot:

"Now is it true, or is it not,

"That what is which and which is what?"

(From work of A. A. Milne)

(a)

What is the output of the following program:

import ccj.*;
public class partA
{ public static void main(String[] args)
  { TextInputStream in = new TextInputStream("winnie.hum");
    TextOutputStream out = new TextOutputStream("humming");
    boolean alt = false;
    while (!in.fail()) {  
      String s = in.readLine();
      if (!in.fail()) {
        if ( alt ) {
          out.println(s);
          alt = !alt;
        }
        else {
          System.out.println(s);
          alt = !alt;
        }
      }
    }
  }
}

Screen Output:

LINES WRITTEN BY A BEAR OF VERY LITTLE BRAIN

I wonder to myself a lot:

"That what is which and which is what?"

Contents of humming:

On Monday, when the sun is hot

"Now is it true, or is it not,

(b)

What is the output of the following program:

import ccj.*;
public class partB
{ public static void main(String[] args)
   { TextInputStream in = new TextInputStream("winnie.hum");
     TextOutputStream out = new TextOutputStream("humming");
     int count = 0;
     while (!in.fail()) {  
       String s = in.readLine();
       if (!in.fail()) {
         out.println(s+"\n");
         count++;
       }
     }
     System.out.println("Count is " + count);
  }
}

Screen Output:

Count is 5

Contents of humming:

On Monday, when the sun is hot

I wonder to myself a lot:

"Now is it true, or is it not,

"That what is which and which is what?"

(a)

Label each method and member variable in the class Faces with C if it is a class method or variable, or I if it is an instance method or variable.

public class Faces {
  Faces() {                                     // INSTANCE
    center = new Point(0,0); 
    radius = 5;
    numFaces++;
  }
  Faces(Point p, int r) {                      // INSTANCE
    center = p.clone(); 
    radius = r;
    numFaces++;
  }
  public void move(double dx, double dy) {     // INSTANCE
    center.move(dx,dy);
  }
  public void draw() {                         // INSTANCE
    new Circle(center, r).draw();
    new Point(center.getX() - radius/2, 
              center.getY() + radius/2).draw();
    new Point(center.getX() + radius/2, 
              center.getY() + radius/2).draw();
    new Circle(new Point(center.getX(), 
                         center.getY() - radius/2), 
               radius/4).draw();
  }
  private Point center;                       // INSTANCE
  private Point radius;                       // INSTANCE
  private static int numFaces;                // CLASS
}

(b)

After the following code is run:

    Faces me = new Faces();
    Faces you = new Faces(new Point(3,3), 2);
    Faces him = new Faces();

How many copies are there of the variable center?

3

How many copies are there of the variable numFaces?

1

What is value of the variable numFaces?

3

(a)

What is the ethical dilemma that you face?

(b)

What are three possible ways of dealing with the situation and what are possible ramifications of each?

1969 3

1970 -3

1971 -23

1972 -23

1973 -15

The first number on each line is the year, the second is the budget surplus or deficit in billions of dollars. You may assume that the surplus/deficit is between than -300 to 100 billion dollars.

The output of your program should be a line graph of the data from the file budget.in, where the x-axis is the year and the y-axis is the amount of the surplus/deficit.

import ccj.*;

public class budget extends GraphicsApplet
{
  public void run()
  {
    setcoord(1969,100,1999,300);   //Resize to fit budget data
    
    TextInputStream in = new TextInputStream("budget.in");
                                   //Open data file for reading
    int year = 1969;               //The year in the data file
    int surp_def = in.readInt();   //Get first surplus/deficit
    Point newPoint = new Point(year,surp_def);//to set up initial point
    Point oldPoint;                //Used to save previous point
    
    while ( !in.fail() )
    {
      year++;            
      oldPoint = newPoint;
      surp_def = in.readInt();
      if ( !in.fail() )
      {
        newPoint = new Point(year, surp_def);
        new Line(oldPoint, newPoint).draw();
      }
    }
  }
}

To play a round, you look at the number on the first card (in this case: 4) and reverse that number of cards from left to right. So, we reverse the first 4 cards to get:

5

1

2

4

3

The game stops when the card with 1 reaches the far left.

(The rest of the example game is:

3

4

2

1

5

2

4

3

1

5

4

2

3

1

5

1

3

2

4

5

.)

(a)

Write a recursive function that takes a hand (an array of integers), prints the hand, and if the first card is not 1, plays a round and calls itself with the new hand.

public static void play(int[] hand)
{
  if ( hand.length() != 0)
  {
    //Print the hand:
    for ( int i=0 ; i < hand.length() ; i++)
      System.out.print(hand[i]+ " ");
    System.out.println();
    
    if ( hand[0] != 1 )
    {
      int j;
      int cardsToReverse = hand[0];  //Storage space to do reverse
      int[] temp = new int(CardsToReverse);
      
      //Reverse the cards:
      for ( j=0 ; j < CardsToReverse ; j++ )
        temp[i] = hand[i];
      for ( j=0 ; j < CardsToReverse ; j++ )
        hand[i] = temp[CardsToReverse - i - 1];
      
      //Call the function again:
      play(hand);      
    }
  }
}

(b)

Write a program that prompts the user for the number of cards and the initial hand, and then calls your recursive function.

import ccj.*;

public class CardGame
{
  public static void main(String[] args)
  {
    System.out.print("Enter number of cards:");
    int numCards = Console.in.readInt();
    int[] hand = new int[numCards];
     
    for (int i = 0 ; i < numCards ; i++)
    {
      System.out.print("Enter card "+(i+1) + ": ");
      hand[i] = Console.in.readInt();
    }
    
    play(hand);
  }
}

(a)

Add two buttons to the program below. The first button should have the label Black and change the drawing color to black. The second button should have the label Purple and change the drawing color to purple.

// This example is modified from the book "Java in a Nutshell" 
// David Flanagan, O'Reilly & Associates, 1996.

import java.applet.*;	//Load in the applet class
import java.awt.*;	//Load in buttons and friends 

public class OneColorDraw extends Applet {
  private int last_x = 0;	//Keep track of x and y coordinate
  private int last_y = 0;	//When the mouse is clicked
  private Color current_color = Color.black;	//Current color
  private Button clear_button;	//Declare space for the clear button
  
  
//ADDED to store buttons:
private Button black_button;
private Button purple_button;
    
  // This function is called initially, when the program begins
  // executing.  It initializes the graphics window.
    
  public void init() {
    this.setBackground(Color.white);   //Set the background color
  
    // Create a button and add it to the graphics window
    clear_button = new Button("Clear");//Make label say "Clear"
    clear_button.setForeground(Color.black);
    clear_button.setBackground(Color.lightGray);
    this.add(clear_button);	//Necessary to use the button
    
//ADDED:
black_button = new Button("Black");//Make label say "Black"
black_button.setForeground(Color.black);
black_button.setBackground(Color.lightGray);
this.add(black_button);	//Necessary to use the button
purple_button = new Button("Purple");//Make label say "Purple"
purple_button.setForeground(Color.black);
purple_button.setBackground(Color.lightGray);
this.add(purple_button);	//Necessary to use the button
    
       
  }
    
  // Called when the user clicks the mouse to start a scribble
  // Sets the values of variables last_x and last_y to mark the
  // point of the click.
    
  public boolean mouseDown(Event e, int x, int y)
  {
    last_x = x; last_y = y;//Store coordinates when mouse clicked
    return true;	//and don't do anything else (that is, the
        		//"event handled" is true)
  }
    
// Continued on the next page -->

  // Called when the user draws with the mouse button down
  // Draws a line between the points (last_x, last_y) and (x, y)
    
  public boolean mouseDrag(Event event, int x, int y)
  {
    Graphics g = this.getGraphics(); //Necessary to draw 
    g.setColor(current_color);	 //Line will be current_color
    g.drawLine(last_x, last_y, x, y);//Draws the line
    last_x = x;	//Saves (x,y) in last (last_x, last_y), so that
    last_y = y;	//the next line drawn will start from these points
    return true;	//and don't do anything else ("event handled").
  }

  // Called when the user clicks the Clear button, and 
  // clears the graphics window.
    
  public boolean action(Event event, Object arg) {
    //If Clear button was clicked, clear graphics window
    if (event.target == clear_button) {
      Graphics g = this.getGraphics();
      Rectangle r = this.bounds();
      g.setColor(this.getBackground());
      g.fillRect(r.x, r.y, r.width, r.height);
      return true;
    }
    
//ADDED:
else if (event.target == black_button)
{
  current_color = Color.black;
  return true;
}
else if (event.target == purple_button)
{
  current_color = Color.purple;
  return true;
}
    
    // Otherwise, let the superclass handle it.
    else return super.action(event, arg);
  }
}

(b)

Add square root, sqrt, to the expr package below. sqrt returns the square root of its argument.

package expr;
import ccj.*;

public class Expression
{ public Expression(String expr)
  { parser = new Parser(expr);
    opstack = new java.util.Stack();
    numstack = new java.util.Stack();
  }
  public double eval()
  { while (true)
    { int type = parser.nextTokenType();
      String s = parser.nextToken();
      if (type == Parser.OPERATOR)
      { if (opstack.empty())
          opstack.push(s);
        else
        { String old = (String)opstack.pop();
          if (Parser.precedence(s) > Parser.precedence(old))
            opstack.push(old);
          else
            evalOperator(old);
          opstack.push(s);
        }
      }
      else if (type == Parser.LEFT_PAREN)
        opstack.push(s);
      else if (type == Parser.RIGHT_PAREN)
      { boolean more = true;
          while (more)
          { if (opstack.empty())
              throw new IllegalArgumentException("Too many )");
            String old = (String)opstack.pop();
            if (old.equals("(")) more = false;
            else evalOperator(old);
          }
      }
      else if (type == Parser.END_OF_STRING)
      { while (!opstack.empty())
          { String old = (String)opstack.pop();
            if (old.equals("("))
              throw new IllegalArgumentException("Too many (");
            else evalOperator(old);
          }
          if (numstack.empty())
            throw new IllegalArgumentException("Syntax error");
          double x = Numeric.parseDouble((String)numstack.pop());
         
          if (!numstack.empty())
            throw new IllegalArgumentException("Syntax error");
          return x;
      }
      else if (type == Parser.NUMBER)
        numstack.push(s);
      else
        throw new IllegalArgumentException("Bad token");
    }
  }

  private void evalOperator(String op)
  { if (numstack.empty())
      throw new IllegalArgumentException("Syntax error");
    double y = Numeric.parseDouble((String)numstack.pop());
    if (numstack.empty())
      throw new IllegalArgumentException("Syntax error");
      
      
//ADDED:
if (op.equals("sqrt") 
{
  if (x < 0)
    throw new IllegalArgumentException("Negative square root");
  z = Math.sqrt(x);
  numstack.push("" + z);
  return;
}
    
    double x = Numeric.parseDouble((String)numstack.pop());

    double z;
    if (op.equals("^")) z = Math.pow(x, y);
    else if (op.equals("*")) z = x * y;
    else if (op.equals("/"))
    { if (y == 0)
        throw new IllegalArgumentException("Divide by 0");
      else z = x / y;
    }
    else if (op.equals("+")) z = x + y;
    else if (op.equals("-")) z = x - y;
    else
      throw new IllegalArgumentException("Bad token");
    numstack.push("" + z);
  }

  private java.util.Stack opstack;
  private java.util.Stack numstack;
  private Parser parser;
}

class Parser
{ Parser(String toParse)
  { input = toParse;
    pos = 0;
  }

  public int nextTokenType()
  { skipWhiteSpace();
    if (pos >= input.length()) return END_OF_STRING;
    String ch = input.substring(pos, pos + 1);
    if (ch.equals("(")) return LEFT_PAREN;
    if (ch.equals(")")) return RIGHT_PAREN;
    if ("+-*/^".indexOf(ch) != -1) return OPERATOR;
    if ("1234567890".indexOf(ch) != -1) return NUMBER;
    
//ADDED:
if (ch.equals("sqrt")) return OPERATOR;
    
    return BAD_TOKEN;
  }

  public String nextToken()
  { int i = nextTokenType();
    if (i == END_OF_STRING || i == BAD_TOKEN) return "";
    if (i == NUMBER)
    { int end = pos + 1;
      boolean more = true;
      while (more && end < input.length())
        { String ch = input.substring(end, end + 1);
          if (ch.equals(".") || "1234567890".indexOf(ch) != -1)
             end++;
          else
             more = false;
        }
      String r = input.substring(pos, end);
      pos = end;
      return r;
    }
    else
    { 

//ADDED:
if ( input.substring(pos,pos+4).equals("sqrt") )
{
  String r = input.substring(pos, pos + 4);
  pos = pos + 4;
  return r;
}

      String r = input.substring(pos, pos + 1);
      pos++;
      return r;
    }
  }

   
  public static int precedence(String operator)
  { if (operator.equals("+") || operator.equals("-")) 
      return 1;
    if (operator.equals("*") || operator.equals("/")) 
      return 2;
    if (operator.equals("^")) return 3;
    
//ADDED:
if (operator.equals("sqrt") return 4;
    
    return 0; 
  }

  public static final int OPERATOR = 1;
  public static final int NUMBER = 2;
  public static final int LEFT_PAREN = 3;
  public static final int RIGHT_PAREN = 4;
  public static final int END_OF_STRING = 5;
  public static final int BAD_TOKEN = 6;

  private void skipWhiteSpace()
  { while (pos < input.length() 
      && input.substring(pos, pos + 1).equals(" "))
        pos++;
  }

  private String input;
  private int pos;
}

Your design needs to include the definitions of the data for the class, the javadoc comments and definitions for the methods including constructors. Do NOT write the code for any of the methods!

The definitions for the data:

  private String first;
  private String middle;
  private Strirng last;
  private int[] quizes;
  private int[] programs;
  private int[] exams;

A constructor with javadoc comment:
/**
 * The default constructor which allocates space for 10 quizzes,
 * 30 programs, and 4 exams.  Sets all strings to null and all 
 * numbers to 0
 **/
public GradeBook()

A method with javadoc comment:

/**
 * Calculates and returns the grade using the following 
 * formula: .2*(quiz total) + .4*(program total) + .4*(exam total).
 * Each total is calculated by summing up the values in the array
 * and dividing by the length. 
 *
 * @return the overall grade (which ranges from 0 to 100)
 **/
public double CalculateGrade()