HW Set 2 - thecubscientist.com

AP Computer Science
Homework Set 2
Class Design
P2A. Write a class Song that stores information about a song. Class Song should
include at least three instance variables that represent characteristics of the song.
Include a zero-argument and three-argument constructor to initialize all instance
variables. It should also have a toString() method to display the object’s instance
variables in a user-friendly format.
Write a separate “SongDriver” class to:
a) create an instance of a Song called “song1” using its zero-argument
constructor,
b) display the instance variables of the “song1” using the object’s
toString() method,
c) create an instance of a Song called a “song2” and initialize its instance
variables using the object’s multi-argument constructor, and
d) display the instance variables of the “song2” using the object’s
toString() method.
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P2B. Write a class Clock that stores information about a clock. It should have
integer instance variables for the Clock’s hours, minutes, seconds. Include a zeroargument
and three-argument constructor to initialize all instance variables. It should
also have a toString() method to display the time in the format shown below:
The time is 3:45:16
Note that zero-argument constructors should initialize instance variables to known
values, most commonly zero for integers, “” for Strings, or false for boolean values.
See the example below:
public Clock()
{
int hour = 0;
double cost = 0.0;
String brand = new String(“”);
boolean isOn = false;
} // end constructor Clock
Write a separate “ClockDriver” class to:
a) create an instance of a Clock called “kitchenClock” using its zeroargument
constructor,
b) display the time of the “kitchenClock” using its toString() method,
c) create an instance of a Clock called a “bedroomClock” and set the hours,
minutes, and seconds using the Clock’s three-arguments constructor using a
JOptionPane, and
d) display the time of the “bedroomClock” using its toString() method.
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P2C. Let’s write another class and test it with a driver. This time let’s create a
Student class that models a Loyola student. The Student class should have
instance variables for the student’s first and last name, and at least TWO other
instance variables chosen by you. Include a zero-argument and multi-argument
constructor to initialize all instance variables. Choose the most appropriate variable
types (i.e. int, double, String, boolean) for each instance variable. It should also have
a toString() method to display the object’s instance variables in a user-friendly
format.
Write a separate “StudentDriver” class to:
a) create an instance of a Student called “senior001” using its zeroargument
constructor,
b) display the instance variables of the “senior001” using the object’s
toString() method,
c) create an instance of a Student called a “frosh001” and initialize its instance
variables using the object’s multi-argument constructor, and
d) display the instance variables of the “frosh001” using the object’s
toString() method.
If you are looking for an extra challenge, try to printout the results of the program
using JOptionPane.showMessageDialog(). See the LewTube video for this
HW Set on the details of how to use this very cool tool (no rhyme intended.)
P2D. Design a class that models an object of your choice (e.g. type of car, sports
team, musical instrument, etc.) Include at least two different instance variables of two
different types (e.g. String and an int, int and a double, boolean and a String, etc.) for
your class. It should also have a toString() method to display the object’ instance
variables in a user-friendly format.
Write a separate “YourObjectDriver” class to:
a) create an instance of a your object called “obj1” (or a name more appropriate
for your object) using its zero-argument constructor,
b) display the instance variables of the “obj1” using the object’s toString()
method,
c) create an instance of a your object called a “obj2” and initialize its instance
variables using the object’s multi-argument constructor, and
d) display the instance variables of the “obj2” using the object’s toString()
method.
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P2E. Blackjack! Design a class called “Card” that models a playing card. Decide
what instance variables you will need for your class in order to play Blackjack (or
any other card game.) Include a zero-argument constructor and the appropriate multiargument
constructor for your class. It should also have a toString() method to
display ALL of the object’s instance variables in a user-friendly format…this can be
a bit tricky…
Write a CardDriver that will perform the following tasks:
a) Create three Card objects: a blank card (i.e. a Card created using its zeroargument
constructor), a “number” card, and a “face” card…you pick the
cards.
b) Create an array called “myHand” that can hold 3 Card objects.
Below are the lines of code that demonstrate how to create an array of Card objects
and how to place a Card object into an array called myHand.
Card[] myHand = new Card[10];
Card card1 = new Card( 10, “Jack”, “Hearts” );
myHand[0] = card1;
c) Use a for loop to traverse the array of your Cards and print each Card using
System.out.println().
The following programs DO NOT need a separate class and driver files. They
are stand-alone programs that are meant to review previous topics (and
introduce a couple of new non-class concepts)
P2F. Write a program that creates an array that can hold 9 double values that
represent baseball batting averages for a starting baseball lineup. Use a for loop to
populate array with double values in the range of 0.00 to 0.500. Recall that “double”
values are what Java calls “real” numbers. Use a second for loop to print the values in
the array with one number per line. Finally, use a third for loop to traverse the array
and find and print the maximum batting average in the array. See the LewTube for
this HW assignment to see how to control the precision of a double number when you
print it.
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P2G. College application time! Write a program that creates an array of Strings. Fill
the array with the name of the universities that you will be applying to. Then perform
the following tasks:
a. traverse the array using a for loop and printout the length of each university’s
name.
You can find the length of a String as shown below:
String name = new String( “UCLA” );
System.out.println( name.length() ); // prints “4”
b. print the name of the university that has the shortest length.
c. You’ve decided not to apply to one of the schools on your list. Remove that
school from the list by setting that element in the array to “null”. This can be
done as shown below:
school[3] = new String( “NYU” );
school[3] = null; // null “removes” NYU from array
d. print your list of schools again using a second for loop.
P2H. Let’s upgrade out “Login” program from HW Set 1 so that it will allows the
user to input a username/password combination for a total of three attempts. If
incorrect on the fourth attempt, the program should print out the following message:
“You have exceeded your three attempts.
Please try again next period.”
Hint: Use a loop along with a counter to count the number of unsuccessful attempts.
By the end of the lesson students should be able to:
a. Write the Java code define a class, its data members, and its constructors.
b. Write a toString() method for a class.
c. Write the Java code that uses the “new” operator to instantiate an object.
d. Write the Java code for a “driver” class that creates instance of an object and
initializes the class’ instance variables and calls the class’ toString()
method.
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