Download Review Exercises

Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
Review Exercises
R5.1
- if quarters > 0 then System.out.println(quarters + " quarters");
Missing parentheses (quarters > 0 ) and illegal keyword then
- if (1 + x > Math.pow(x, Math.sqrt(2)) y = y + x;
Unbalanced parentheses around condition, use:
if (1 + x > Math.pow(x, Math.sqrt(2))) y = y + x;
- if (x = 1) y++; else if (x = 2) y = y + 2;
(x = 1) and (x = 2) are assignments, not comparisons, use (x == 1)
and (x == 2) instead.
- if (x && y == 0) { x =1; y =1; }
Incompatible variable types: If x, y are integers, logical operations like && can not be
performed on them. If x, y are boolean, they can't be compared to 0. Use the following
instead:
if (x == 0 && y == 0) . . .;
-if (1 <= x <= 10)
System.out.println(x);
Invalid condition, use if(1 <= x && x <= 10)
- if (s != "nickels" || s != "pennies"
|| s != "dimes" || s != "quarters")
System.out.print("Input error !");
instead.
There is no way for the condition to evaluate true. s cannot simultaneously be nickels,
pennies, dimes or quarters. If s must be one of the choices, use the following
instead:
if (s != "nickels" && s != "pennies"
&& s != "dimes" && s != "quarters")
System.out.print("Input error !");
- if (input.equalsIgnoreCase("N") || "NO")
return;
Invalid compund condition, use the following instead:
if (input.equalsIgnoreCase("N") || input.equalsIgnoreCase("NO"))
. . .
- int x = Integer.parseInt(input);
if (x != null) y = y + x;
The integer value x can never be null. Use
if (input != null) y = y + Integer.parseInt(input);
- language = "English"
if (country.equals("USA"))
if (state.equals("PR")) language = "Spanish";
else if (country.equals("China"))
language = "Chinese";
1
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
2
The indentation levels give the wrong impression: the else actually pairs with the closest
if. Use parentheses:
language = "English"
if (country.equals("USA"))
{ if (state.equals("PR")) language = "Spanish";
}
else if (country.equals("China"))
language = "Chinese";
R5.3
In Java if/else if /else statements are used to express a multiple alternative, in
which exactly one from a mutually exclusive set of choices is selected to be executed.
Nested if statements are used to express a selection from multiple alternatives when
there are multiple conditions for each selection.
/* value of integer choice used to select one of four possible values
for x */
if (choice == 1) x = n;
else if (choice == 2) x = n * n;
else if (choice == 3) x = n * n * n;
else x = -2;
/* value of integer choice and value of boolean available
used to select one of four possible values for x */
if (choice == 1)
{ if (x > 0)
x = n;
else
x = n * n;
}
else
{ if (x > 0)
x = n * n * n;
else
x = -2;
}
R5.5
First
Dick
Tom
Churchill
car manufacturer
Harry
C++
Tom
Car
bar
R5.7
Second
Tom
Tomato
church
carburetor
hairy
car
Tom
Carl
car
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
3
There is no level at which a tax payer ends up with less money if they have a higher
income. The income tax is progressive in that higher incomes are taxed at higher rate, but
that higher tax rate is applied only to the amount earned above the maiximum level that
can be taxed at each preceding lower rate. For example, if you earn $21,460, the first
$21,450 are taxed at the lower level of 15%, then the remaining $10 are taxed at the
higher 28% rate.
If a married couple files jointly and together earn between $35,800 and $42,900, or
between $86,500 and $103,800, they will have to pay a higher tax than if they'd filed
separately if they are earning the same amount.
R5.9
In the first block, the conditions are evaluated sequentially, so s could be incremented
twice. In the second block, the conditional statements are mutually exclusive, so, s
cannot be incremented more than once.
R5.11
status = "GOOD";
if (GPA >= 1.5)
if (GPA < 2.0)
status = "PROBATION";
else
status = "FAILING";
Should be:
status = "GOOD";
if (GPA >= 1.5)
{ if (GPA < 2.0)
status = "PROBATION";
}
else
status = "FAILING";
or better:
if (GPA >= 2.0)
status = "GOOD";
else if (GPA >= 1.5)
status = "PROBATION";
else
status = "FAILING";
}
R5.13
r == s
tests whether r and s are references to the identical Rectangle object.
r.equals(s)
tests whether r and s are rectangles with the same coordinates.
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
R5.15
For the lexicographic comparison, upper- and lowercase are distinguished. Also, "filler
characters" such as . - and space are used in the comparison, whereas they would be
ignored in the phonebook
Lexicographic ordering is like a dictionary alphabetic ordering, but some of the
characters have different values which results in their being sorted into a different
position. Specifically, all white space (space, horizontal tab, vertical tab, carriage return
and line feed) precede digits (0-9) which precede uppercase letters (A-Z) which precede
lowercase letters(a-z). The sort order of punctuation and other printing characters is less
intuitive.
R5.17
To test if an integer equals ten use:
int n ;
if(n == 10) . . .
To test if a floating point number equals ten use:
double denom = Math.abs(x);
if(Math.abs(y) < 10) denom = 10;
if((Math.abs(x - 10) / denom) <= EPSILON ) . . .
R5.19
Marital
Status
S
S
S
S
S
M
M
M
M
M
Income Tax
-1
none
0
none
21000 3150.00
(21450).15 + (25000-21450).28 = 3217.00 + 994.00
25000 =
4211.00
(21450).15 + (51900 - 21450).28 + (6000060000
51900).31 = 3217.00 + 994.00 + 2511.00 = 6722.00
-1
none
0
none
35000 5250.00
(35800).15 + (57000-35800).28 = 5370.00 +
57000 5936.00 =
11306.00
(35800).15 + (86500 - 35800).28 + (9000090000 86500).31 = 5370.00 + 14196.00 + 1085.00 =
20651.00
Programming Exercises
4
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
P5.1
QuadraticEquation.java
public class QuadraticEquation
{
/**
Constructs a quadratic equation and get 2 solutions
@param coefficientA coefficient a of quadratic equation
@param coefficientB coefficient b of quadratic equation
@param coefficientC coefficient c of quadratic equation
*/
public QuadraticEquation(double coefficientA, double coefficientB,
double coefficientC)
{
a = coefficientA;
b = coefficientB;
c = coefficientC;
discriminant = b * b - 4 * a * c;
}
/**
Returns the first solution to the quadratic equation
@return the first solution
*/
public double getSolution1()
{
return (-b + Math.sqrt(discriminant)) / (2 * a);
}
/**
Returns the second solution to the quadratic equation
@return the second solution
*/
public double getSolution2()
{
return (-b - Math.sqrt(discriminant)) / (2 * a);
}
/**
Determines if there is a solution or not
@return true if there is a solution
*/
public boolean hasSolutions()
{
return (discriminant > 0);
}
double
double
double
double
}
a;
b;
c;
discriminant;
5
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
QuadraticEquationTest.java
/**
This program tests the QuadraticEquation class.
*/
import javax.swing.JOptionPane;
public class QuadraticEquationTest
{
public static void main(String[] args)
{
String input = JOptionPane.showInputDialog(
"Please enter coefficient a:");
int a = Integer.parseInt(input);
input = JOptionPane.showInputDialog(
"Please enter coefficient b:");
int b = Integer.parseInt(input);
input = JOptionPane.showInputDialog(
"Please enter coefficient c:");
int c = Integer.parseInt(input);
QuadraticEquation myEquation = new QuadraticEquation(a, b, c);
if(myEquation.hasSolutions())
{
System.out.println(myEquation.getSolution1());
System.out.println(myEquation.getSolution2());
}
else
System.out.println("There are no solutions.");
System.exit(0);
}
}
P5.3
LabeledPoint.java
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
/**
A point with a label showing the point's coordinates.
*/
public class LabeledPoint
{
/**
Construct a labeled point.
@param anX the x-coordinate
@param aY the y-coordinate
*/
public LabeledPoint(double anX,double aY)
6
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
{
x = anX;
y = aY;
}
/**
Draws the point as a small circle with a coordinate label.
@param g2 the graphics context
*/
public void draw(Graphics2D g2)
{
//draw a small circle centered around (x, y)
Ellipse2D.Double circle = new Ellipse2D.Double(
x - SMALL_CIRCLE_RADIUS,
y - SMALL_CIRCLE_RADIUS,
2 * SMALL_CIRCLE_RADIUS,
2 * SMALL_CIRCLE_RADIUS);
g2.draw(circle);
//draw the label
String label ="("+ x + "," + y + ")";
g2.drawString(label, (float)x, (float)y);
}
private static final double SMALL_CIRCLE_RADIUS = 2;
private double x;
private double y;
}
IntersectionApplet.java
import
import
import
import
import
import
java.applet.Applet;
java.awt.Graphics;
java.awt.Graphics2D;
java.awt.geom.Ellipse2D;
java.awt.geom.Line2D;
javax.swing.JOptionPane;
/**
An applet that computes and draws the intersection points
of a circle and a line.
*/
public class IntersectionApplet extends Applet
{
public IntersectionApplet()
{
String input
= JOptionPane.showInputDialog("x:");
x = Integer.parseInt(input);
}
7
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
/**
Method to draw the circle and compute the intersection points
*/
public void paint(Graphics g)
{
Graphics2D g2 = (Graphics2D)g;
//draw the circle
Ellipse2D.Double circle = new
Ellipse2D.Double(0, 0, 2 * RADIUS, 2 * RADIUS);
g2.draw(circle);
//draw the vertical line
Line2D.Double line
= new Line2D.Double(x, 0, x, 2 * RADIUS);
g2.draw(line);
//compute the intersection points
double a = RADIUS;
double b = RADIUS;
double discriminant = RADIUS * RADIUS - (x - a) * (x - a);
if (discriminant < 0)
{
System.out.println("Error: No Intersection");
}
double root = Math.sqrt(discriminant);
double y1 = b + root;
double y2 = b - root;
//draw the intersection points
LabeledPoint p1 = new LabeledPoint(x, y1);
LabeledPoint p2 = new LabeledPoint(x, y2);
p1.draw(g2);
p2.draw(g2);
}
private static final double RADIUS = 100;
private static final double DIAMETER = RADIUS * 2;
private double x;
}
P5.5
Circle.java
import java.awt.Graphics2D;
import java.awt.geom.Point2D;
import java.awt.geom.Ellipse2D;
8
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
/**
This class implements a circle and a boolean function to
test if a user-given point is inside this circle
*/
public class Circle
{
/**
Constructs a circle and a point
@param x the x-coordinate
@param y the y-coordinate
*/
public Circle(double x, double y)
{
xLeft = x;
yTop = y;
}
/**
Draws a circle and a point
@param g2 the graphics content
*/
public void draw(Graphics2D g2)
{
// draw the circle with center (110, 120)
final double CENTERX = 110;
final double CENTERY = 120;
Ellipse2D.Double circle
= new Ellipse2D.Double(CENTERX - RADIUS , CENTERY - RADIUS,
2 * RADIUS, 2 * RADIUS);
g2.draw(circle);
// draw the point
Ellipse2D.Double point
= new Ellipse2D.Double(xLeft - 1, yTop - 1, 3, 3);
g2.draw(point);
}
/**
Determine if point is inside or outside the circle
@param p the point to test if it is inside the circle
@return true if the point is inside the circle
*/
public boolean isInside(Point2D.Double p)
{
double dx = xLeft - RADIUS;
double dy = yTop - RADIUS;
return ((dx * dx + dy * dy) <= (RADIUS * RADIUS));
}
private static final double RADIUS = 100;
private double xLeft;
9
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
private double yTop;
}
ExP5_5.java
import
import
import
import
import
import
java.applet.Applet;
java.awt.Graphics;
java.awt.Graphics2D;
java.awt.geom.Point2D;
java.awt.geom.Ellipse2D;
javax.swing.JOptionPane;
/**
This class tests class Circle to determine if a point
is inside a circle with center(110, 120)
*/
public class ExP5_5 extends Applet
{
public void init()
{
String input =
JOptionPane.showInputDialog("x:");
x = Integer.parseInt(input);
input =
JOptionPane.showInputDialog("y:");
y = Integer.parseInt(input);
}
public void paint(Graphics g)
{
Graphics2D g2 = (Graphics2D)g;
Circle circle = new Circle(x, y);
circle.draw(g2);
String message;
Point2D.Double point
= new Point2D.Double(x, y);
if(circle.isInside(point))
message = "Congratulations";
else
message = "You missed.";
JOptionPane.showMessageDialog(null, message);
}
private double x;
private double y;
}
P5.7
InputChecker.java
/**
This class checks if the user wants to continue
10
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
*/
public class InputChecker
{
/**
Constructs an input checker to determine if user
wants to continue
@param anInput the input of the user
*/
public InputChecker(String anInput)
{
input = anInput;
result = 0;
}
/**
Checks the user's input
@result the result of checking the input
*/
public int checkInput()
{
if (input.equalsIgnoreCase("Y") ||
input.equalsIgnoreCase("Yes") ||
input.equalsIgnoreCase("Sure") ||
input.equalsIgnoreCase("Why not?") ||
input.equalsIgnoreCase("OK"))
result = 1;
else if (input.equalsIgnoreCase("N") ||
input.equalsIgnoreCase("No"))
result = -1;
return result;
}
/**
Test if the user wants to continue
@return true the user wants to continue
*/
public boolean isYes()
{
return (checkInput() > 0);
}
/**
Test if the user does not want to continue
@return true the user does not want to continue
*/
public boolean isNo()
{
return (checkInput() < 0);
}
private String input;
private int result;
}
11
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
ExP5_7.java
import javax.swing.JOptionPane;
/**
This tests the InputChecker class
*/
public class ExP5_7
{
public static void main(String[] args)
{
String input = JOptionPane.showInputDialog(
"Do you want to continue?");
InputChecker c = new InputChecker(input);
if(c.isYes())
System.out.println("OK");
else if (c.isNo())
System.out.println("Terminating");
else
System.out.println("Bad Input");
System.exit(0);
}
}
P5.9
Grade.java
/**
This class finds the letter representation of a numeric grade
*/
public class Grade
{
/**
Constructs a letter grade
@param numericGrade the numeric grade given by user
*/
public Grade(double numericGrade)
{
input = numericGrade;
}
/**
Find the letter grade from a numeric grade
@return grade the letter grade
*/
public String getLetterGrade()
{
String letter = "";
String mod= "";
if (input >= 0 && input <= 4.5)
12
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
{
if (input >= 3.5 )
letter = "A";
else if (input >= 2.5 )
letter = "B";
else if (input >= 1.5 )
letter = "C";
else if (input >= 0.5 )
letter = "D";
else
letter = "F";
}
else
letter = "That is not valid";
double remainder = input - (int)input;
if ((0.5 <= remainder) && (remainder < 0.85))
mod = "-";
else if ((0.15 <= remainder) && (remainder < 0.5))
mod = "+";
return letter + mod;
}
private double input;
}
ExP5_9.java
import javax.swing.JOptionPane;
/**
This class tests the class Grade to find a letter representation
of a numeric grade
*/
public class ExP5_9
{
public static void main(String[] args)
{
String input = JOptionPane.showInputDialog(
"Enter a numeric grade:");
double numGrade = Double.parseDouble(input);
Grade g = new Grade(numGrade);
System.out.println(g.getLetterGrade());
System.exit(0);
}
}
P5.11
TaxReturn.java
/**
Class TaxReturn is used to determine the tax amount for a person
13
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
*/
public class TaxReturn
{
/**
Constructs an object TaxReturn
@param anIncome of a person
@param aStatus of a person...i.e. single or married
*/
public TaxReturn(double anIncome, String aStatus)
{
income = anIncome;
status = aStatus;
}
/**
Method used to determine the status of a person
and calculate the tax
@return the tax amount
*/
public double getTax()
{
double tax = 0;
final double RATE1 = 0.15;
final double RATE2 = 0.28;
final double RATE3 = 0.31;
final double SINGLE_CUTOFF1 = 21450;
final double SINGLE_CUTOFF2 = 51900;
final double SINGLE_BASE2 = 3217.50;
final double SINGLE_BASE3 = 11743.50;
final double MARRIED_CUTOFF1 = 35800;
final double MARRIED_CUTOFF2 = 86500;
final double MARRIED_BASE2 = 5370;
final double MARRIED_BASE3 = 19566;
double cutoff1;
double cutoff2;
if (status.equalsIgnoreCase("S"))
{
cutoff1 = SINGLE_CUTOFF1;
cutoff2 = SINGLE_CUTOFF2;
}
else /* status is M */
{
cutoff1 = MARRIED_CUTOFF1;
cutoff2 = MARRIED_CUTOFF2;
}
if (income < cutoff1)
tax = RATE1 * income;
else if (income < cutoff2)
14
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
15
tax = RATE1 * cutoff1 + (income - cutoff1) * RATE2;
else
tax = RATE1 * cutoff1 + RATE2 * (cutoff2 - cutoff1)
+ RATE3 * (income - cutoff2);
return tax;
}
private double income;
private String status;
}
ExP5_11.java
import javax.swing.JOptionPane;
/**
This is test class for TaxReturn class
*/
public class ExP5_11
{
public static void main(String[] args)
{
String input = JOptionPane.showInputDialog(
"Please enter your income:");
double income = Double.parseDouble(input);
String status = JOptionPane.showInputDialog(
"Please enter S for single, M for married:");
TaxReturn aTaxReturn = new TaxReturn(income, status);
System.out.println("The tax is " + aTaxReturn.getTax());
System.exit(0);
}
}
5.13
Month.java
/**
This class determines the number of days in a month
*/
public class Month
{
/**
Creates a Month object to determine the number of days in a month
@param aMonth is the month in numeric format to determine the
number of days
*/
public Month(int aMonth)
{
month = aMonth;
}
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
/**
Method to get the number of days in the month
@return the days in the tested month
*/
public int getDays()
{
int days;
if (month == 4 || month == 6 || month == 9 || month == 11)
days = 30;
else if (month == 2)
days = 28;
else if (1 <= month && month <= 12)
days = 31;
else
days = -1;
return days;
}
private int month;
}
ExP5_13.java
import javax.swing.JOptionPane;
/**
This is a test driver class for Month class
*/
public class ExP5_13
{
public static void main(String[] args)
{
String input = JOptionPane.showInputDialog(
"Please enter the number of a month:");
int month = Integer.parseInt(input);
Month m = new Month(month);
int days = m.getDays();
if (days < 0)
System.out.println("ERROR: Bad Input");
else
System.out.println(days + " days");
System.exit(0);
}
}
P5.15
BankAccount.java
/**
A bank account has a balance that can be changed by
16
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
deposits and withdrawals.
*/
public class BankAccount
{
/**
Constructs a bank account with a zero balance.
*/
public BankAccount()
{
balance = 0;
}
/**
Constructs a bank account with a given balance.
@param initialBalance the initial balance
*/
public BankAccount(double initialBalance)
{
if (initialBalance >= 0)
balance = initialBalance;
}
/**
Deposits money into the bank account.
@param amount the amount to deposit
*/
public void deposit(double amount)
{
if (amount >= 0)
{
double newBalance = balance + amount;
balance = newBalance;
}
}
/**
Withdraws money from the bank account.
@param amount the amount to withdraw
*/
public void withdraw(double amount)
{
if (amount <= balance)
{
double newBalance = balance - amount;
balance = newBalance;
}
}
/**
Gets the current balance of the bank account.
@return the current balance
*/
public double getBalance()
{
return balance;
}
17
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
private double balance;
}
ExP5_15.java
import javax.swing.JOptionPane;
/**
This is a test driver class for BankAccount class
*/
public class ExP5_15
{
public static void main(String[] args)
{
String input = JOptionPane.showInputDialog(
"Enter deposit:");
double dep = Double.parseDouble(input);
input = JOptionPane.showInputDialog(
"Enter withdrawal:");
double wit = Double.parseDouble(input);
BankAccount account = new BankAccount();
account.deposit(dep);
account.withdraw(wit);
System.out.println("Balance is $" + account.getBalance());
System.exit(0);
}
}
P5.17
UnitConverter.java
/**
This class implements a unit converter for
converting from one unit to another
*/
public class UnitConverter
{
/**
Constructs a unit converter to converter
from one unit to another
@param unit the unit to convert either from or to
*/
public UnitConverter(String unit)
{
final double FLUID_OUNCE_TO_LITER = 29586;
final double GALLON_TO_LITER = 3.758;
final double OUNCE_TO_GRAM = 28.3495;
final double POUND_TO_GRAM = 453.6;
final double INCH_TO_METER = 0.0254;
final double FOOT_TO_METER = 0.305;
final double MILE_TO_METER = 1609;
18
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
if (unit.equals("fl.oz"))
factor = FLUID_OUNCE_TO_LITER;
else if (unit.equals("ml"))
factor = 0.001;
else if (unit.equals("l"))
factor = 1;
else if (unit.equals("oz"))
factor = OUNCE_TO_GRAM;
else if (unit.equals("lb"))
factor = POUND_TO_GRAM;
else if (unit.equals("mg"))
factor = 0.001;
else if (unit.equals("g"))
factor = 1;
else if (unit.equals("kg"))
factor = 1000;
else if (unit.equals("in"))
factor = INCH_TO_METER;
else if (unit.equals("ft"))
factor = FOOT_TO_METER;
else if (unit.equals("mi"))
factor = MILE_TO_METER;
else if (unit.equals("mm"))
factor = 0.001;
else if (unit.equals("cm"))
factor = 0.01;
else if (unit.equals("m"))
factor = 1;
else if (unit.equals("km"))
factor = 1000;
else
factor = -1;
}
/**
Converts a measurement to metric
@param measurement the measurement to convert
to metric
@return metric measurement
*/
public double toMetric(double measurement)
{
19
Solutions Manual: Chapter 5
Big Java, by Cay Horstmann
return measurement * factor;
}
/**
Converts a measurement from metric
@param measurement the measurement to convert
from metric
@return measurement that is converted
*/
public double fromMetric(double measurement)
{
return measurement / factor;
}
private String type;
private double factor;
}
ExP5_17.java
import javax.swing.JOptionPane;
/**
This is a test driver for the UnitConverter class
*/
public class ExP5_17
{
public static void main(String[] args)
{
String fromUnit = JOptionPane.showInputDialog(
"Convert from:");
String toUnit = JOptionPane.showInputDialog(
"Convert to:");
UnitConverter from = new UnitConverter(fromUnit);
UnitConverter to = new UnitConverter(toUnit);
String input = JOptionPane.showInputDialog(
"Value:");
double value = Double.parseDouble(input);
double metric = from.toMetric(value);
double converted = to.fromMetric(metric);
if(converted < 0)
System.out.println("ERROR: Bad Input");
else
System.out.println(value + " " + fromUnit +
" = " + converted + " " + toUnit);
System.exit(0);
}
}
20