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Worksheet #1: Stacks Solved
Download and import the file Worksheet1.java. Use the file to answer the following questions.
Please write your answers in the worksheet. Add code to the file to see if it works but do not turn in the code.
1) Notice Worksheet1.java contains the generic stack class from assignment 5 and a Book class. If we wanted to create a stack of books, give a short explanation of what changes, if any, are needed to the generic class to create a stack of books. Give a short reason why. (2pts)
2) Note that the file contains a Book class. What code is needed to create a stack of books? (2 pts)
a. In main, find the comment “Worksheet1 Question #2”
b. At this point, what code is needed to create a stack of books called bookStack? Write code here:
3) What code is needed to add new book object to the bookStack? (2 pts)
c. In main, find the comment “Worksheet1 Question #3”
d. At this point, what code is needed to add a book to the stack? Write that code here:
4) What code is needed to print the name of each book in the bookStack? Use a while loop. (6 pts)
e. In main, find the comment “Worksheet1 Question #4”
f. At this point, write a while loop to print the name of each book. Write that code here:
5) What code is needed to examine the top element on the bookStack? (3 pts)
g. In main, find the comment “Worksheet1 Question #5”
h. At this point, add one line of code to display the book on top of the stack. Write that code here:
i. What error occurs when you add the line in 5h and run the file? Why does this occur?
j.
k.
Worksheet #2: Nested Objects (12 pts)
Download and import the file Worksheet2.java. Use the file to answer the following questions.
1) Let’s create a queue in main. This means, the queue is not nested inside a class. In main, find the comment “Worksheet2 Question #1”
a. At this point, write the declaration for a queue of books and place the books that have been created for you into this queue using the offer method. Write that code here: (2 pt)
2) Next, let’s move the queue inside a class called BookQueue. Complete the BookQueue class below by writing on the worksheet the code required for each method. Find Worksheet2 Question #2. (6 pts)
class BookQueue {
private Queue<Book> queue = new LinkedList<>(); public int size() {
}
public void offer(Book book) {
}
public Book remove() {
}
} // BookQueue
3) Finally, test the BookQueue class using the code in Worksheet2.java
a. Write the declaration for an object of type BookQueue. Place the three books that were created into the object (it acts like a queue!) Find comment Worksheet2 Question #3a. (2 pt)
b. Write the code to print the names of the books in the BookQueue object. Worksheet2 Question #3b. (2 pts)
Worksheet #3: Complicated Nested Objects (20 pts)
Download and import the file Worksheet3.java. Use the file to answer the following questions.
1) Now that you’ve seen how to nest a queue of books inside a class, let’s nest a queue of Scores inside the Player class which will then be placed inside an array. Complete the Player class below by writing on the worksheet the code required for each method. Find comment Worksheet3 Question #1. (6 pts)
class Score {
private int value;
private String dateOfScore;
public Score (int value, String dateOfScore) { this.name = name;
this.dateOfScore = dateOfScore;
}
public int getValue() {
return value;
}
} // Score
class Player {
// Queue of scores for this player
private Queue<Score> scores = new LinkedList<>(); public int getScoresSize() {
}
public void addScore (Score score) {
}
public Score getScore () {
}
} // Player
2) Assume we have a modified PinballMachine class from Assignment 4 and the Player class shown above. An array of player objects has been added. Each player in the array contains a queue as shown above.
class PinballMachine {
private Player[] players; // Array of players whose scores for this // pinball machine are saved
public void addPlayer (Player player, int slot) { players[slot] = player;
}
} // PinballMachine
Draw a picture of a PinballMachine object. Show the array of players and for each player in the array the queue of scores. Assume the pinball machine can store scores for only a small number of players so the player array will have 5 slots (0-4) with the players shown below. Show the following in your picture:
1. Show all slots in the player array, including the ones that do not contain players. (10 pts)
2. Be sure to label the different pieces!
• Slot 0: Frank who has a queue with 4 scores (10,500, 50,000, 45,900, 45,000)
• Slot 3: Paul who has a queue with 2 scores (33133, 80720)
• Slot 4: who has a queue with 3 scores (24900, 44580, 80902)
3) In question 2 above, in order to add a player to the pinball machine’s list of players, we use the addPlayer method. Now, what if we want to add a score to a specific player’s queue of scores?
This process requires thinking through several layers of nested objects, that is:
Pinball machine contains a player array which contains players and each player contains a queue
Write a PinballMachine method called addScoreToPlayer which takes a score object and a slot number. Use the picture above to visualize what needs to be done to add one score to the player’s queue of scores. Find comment Worksheet3 Question #3 and write that code here: (4 pts)
• Add a score to the player in location (slot) in the player array public void addScoreToPlayer(Score score, int slot) {
}
Worksheet #4: Priority Queues and Comparable Interface (23 pts)
Download and import the file Worksheet4.java. Use the file to answer the following questions in the worksheet.
1) When the remove method on a priority queue is called, how does it decide which element to remove? (2 pts)
2) Write the declaration for a priority queue of integers. Write that code here: (2 pts)
3) Write the declaration for a priority queue of player objects. Name this priority queue results. Find comment Worksheet4 Question #3. Write that code here: (2 pts)
4) Let’s do some experimenting in code. In Worksheet4.java you’ll see the Player and Scores classes from Worksheet #3: Complicated Nested Objects with some minor changes to the Player class. After importing the java file, fix the errors by doing the following:
a. In the Player class, complete the getScoresSize, addScores and getScores methods.
i. In Player class, there are 3 comments for “Worksheet4 Question #4a”
ii. Copy the answers from question #1 in Worksheet #3 Complicated Nested Objects to complete these 3 methods.
iii. No need to re-write that code in worksheet for this step.
b. Now, let’s add players to the priority queue called results. (4 pts)
i. In main, find the comment “Worksheet4 Question #4b”
ii. At this point, write code to add player1 & player2 to the priority queue called results. Write that code here:
c. Run the code. What is the result? Show the exact output. (2 pts)
d. The Player class is missing some code that will fix the issue in 4c. Describe the pieces of code that are missing in the Player class? (2 pts)
e. Explain why the code in 4d is necessary. (3 pts)
f. Using the number of scores for a player as the comparison factor, add the necessary code to the Player class in the java file and rerun it. Did the issue in 4c go away? Write that code here: (6 pts)
