Unit 3 Projects

Unit 3 Projects

Each coding exercise has its own folder. Open its .java file and press Run to try it. Run Tests checks every graded exercise in this lesson at once.

These projects were created by Leigh Anne Fitz and Lisa Ferran to provide engaging, standards-aligned learning experiences for AP Computer Science A students. The autograding tests were designed by Kate McDonnell.

Now that you've mastered the fundamentals of Java programming, it's time to begin building your own classes. In these projects, you'll learn how to design classes that model real-world objects by creating instance variables, writing constructors, and implementing methods that define an object's behavior.

Each project is designed to reinforce object-oriented programming through authentic programming tasks. As you complete them, focus on designing classes with clear responsibilities, choosing meaningful names for variables and methods, and testing your classes thoroughly. Well-designed classes are the foundation of organized, reusable, and maintainable programs.

Class Structure Review

A class is a blueprint for creating objects. It defines the data an object has and the actions it can perform.

Basic Class Structure:

public class Student {

    // Instance variables
    private String name;
    private int grade;

    // Constructor
    public Student(String n, int g) {
        name = n;
        grade = g;
    }

    // Method
    public String introduce() {
        return "My name is " + name
          + " and I am in grade " + grade;
    }
}

The Main Parts of a Class

Remember - A useful way to think about a class is:

Class = What it has + What it can do

Example:

• Class: Dog
• What it Has: name, breed, age
• What it Can Do: bark(), run(), eat()

Unit 3 Project 1 - Library Book

A library wants to create a program to keep track of books that students can borrow.

A LibraryBook object represents one book in the library. Each book has a title, an author, and the number of days the book may be borrowed.

The class should provide methods that allow a program to:

• Create a new LibraryBook object.
• Get the title of a book.
• Get the number of days a book may be borrowed.
• Extend the number of days a book may be borrowed.
• Get a description of the book.

The following table shows examples of calls to methods in the LibraryBook class.

LibraryBook Methods

Exercise 1

Write the complete LibraryBook class using the description above.

Open the 01-unit3-project-1 folder and edit Main.java. Press Run to try it; Run Tests checks it (10 tests). Name the class, then rename the file to match.

Unit 3 Project 2 - Game Player

An online game tracks information about each player's performance. A GamePlayer object stores a player's username, the number of games played, the total number of points earned, and whether the player is currently active.

The class should provide methods that allow a program to:

• Create a new GamePlayer object
• Complete a game where it adds the given number of points to totalPoints, increases gamesPlayed by 1, and if the player has completed 20 or more games, set active to false.
• Change the player's status to active
• Get the player's average score (if the player has not completed any games, return 0.0)
• Get the rank of the player:
  • Beginner if the average score is less than 50.
  • Intermediate if the average score is at least 50 but less than 100.
  • Advanced if the average score is 100 or higher.
    • Note: This method must call the method for averaging the score correctly to receive full points
• Get the status of the player (active or not)
• Prints the player object in the form: <username>: Games Played = <gamesPlayed>, Average Score = <average>, Rank = <rank>
  • This method must call the appropriate methods for the average and the rank to receive full points

The following table shows examples of calls to methods in the GamePlayer class.

GamePlayer Methods

Exercise 2

Write the complete GamePlayer class using the description above.

Open the 02-unit3-project2-gameplayer folder and edit Main.java. Press Run to try it; Run Tests checks it (10 tests). Name the class, then rename the file to match.