AP Computer Science a Quiz: Abstraction And Program Design

What this quiz covers

This quiz focuses on Abstraction And Program Design, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Computer Science a.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. manufacturer and screenResolution as class variables; serialNumber and batteryPercentage as instance variables. (correct answer)
2. All four attributes (manufacturer, screenResolution, serialNumber, batteryPercentage) should be designed as instance variables.
3. All four attributes (manufacturer, screenResolution, serialNumber, batteryPercentage) should be designed as class variables.
4. serialNumber as a class variable; manufacturer, screenResolution, and batteryPercentage as instance variables.

Question 2

1. Data encapsulation, which hides the internal state of an object from the outside world.
2. Method overloading, which allows multiple methods to have the same name with different parameter lists.
3. Method decomposition, which breaks down a complex behavior into smaller, manageable procedures. (correct answer)
4. Object instantiation, which is the process of creating a new instance of a class.

Question 3

1. Create multiple overloaded versions of the method, one for each common width and height combination.
2. Change the method's name to calculateAreaOf10x5Rectangle to make its limited purpose more explicit.
3. Add width and height parameters to the method so it can calculate the area for any rectangle, not just one specific size. (correct answer)
4. Keep the method as is, but add extensive comments explaining that it only works for a 10x5 rectangle.

Question 4

1. Because of inheritance, which ensures that changes to a superclass method are automatically applied to all subclasses.
2. Because of procedural abstraction, which separates the method's interface (its signature) from its implementation (its internal logic). (correct answer)
3. Because of polymorphism, which allows an object to take on many forms and behave differently depending on its type.
4. Because of data encapsulation, which bundles the sort method together with the data it operates on.

Question 5

1. An instance variable for the unique ID number and a class variable to store the total count of students. (correct answer)
2. A class variable for the unique ID number and an instance variable to store the total count of students.
3. Both the unique ID number and the total count of students should be stored as instance variables.
4. Both the unique ID number and the total count of students should be stored as class variables.

Question 6

1. An attribute is a synonym for a method's behavior, while an instance variable is a specific type of data storage used only within constructors.
2. An instance variable is a specific type of attribute; its value is unique to each object and helps define that object's state. (correct answer)
3. An attribute is always a class variable shared by all objects, while an instance variable is unique to a single object.
4. An attribute and an instance variable are completely unrelated concepts; attributes relate to design, and instance variables relate to syntax.

Question 7

1. Methods within a single ShoppingApplication class, such as customer(), order(), and product().
2. Parameters for a single constructor, such as public ShoppingApplication(Customer c, Order o, Product p).
3. Separate classes named Customer, Order, and Product, each with its own attributes and behaviors. (correct answer)
4. Private instance variables within the main method of the application, used to track the application's current state.

Question 8

1. The actions accelerate and brake, which directly modify the car's state.
2. The properties color and currentSpeed, which describe the car's state. (correct answer)
3. The class name Car and the property color, which are fundamental to its identity.
4. The action accelerate and the property color, representing one behavior and one state.

Question 9

1. The properties accountNumber and balance, which describe the account's state.
2. The action deposit and the property accountNumber, representing a behavior and a state.
3. The actions deposit and withdraw, which modify the account's state. (correct answer)
4. The action withdraw and the property balance, representing a behavior and a state.

Question 10

1. This design phase automatically generates all the required Java code from the diagrams, which eliminates the need for manual programming.
2. These diagrams are compiled by the Java compiler to check for syntax errors before any code is actually written.
3. This phase allows the team to plan the program's overall structure, define responsibilities for each class, and manage complexity before investing time in implementation. (correct answer)
4. The diagrams created in this phase serve as the final, official user manual for the customers of the completed software.

Question 11

1. Methods like getArea() always execute faster than retrieving the value of an instance variable, improving program performance.
2. This design ensures data consistency; if the radius is changed, the values returned by getArea() and getCircumference() will be correct without needing to manually update other variables. (correct answer)
3. It is not possible in Java to store calculated floating-point values, such as area or circumference, as instance variables; they must be calculated in methods.
4. Storing area and circumference as instance variables would violate encapsulation and require making the radius variable public for them to be calculated.

Question 12

1. Iteration, which involves the process of repeating a set of instructions multiple times to accomplish a task.
2. Abstraction, which involves providing a simplified interface that hides complex underlying implementation details. (correct answer)
3. Variable declaration, which involves the process of assigning a symbolic name to a specific location in computer memory.
4. Conditional logic, which allows a program to make decisions and execute different code paths based on specific criteria.

Question 13

1. The resulting program is often easier for other programmers to read and understand.
2. These design principles entirely eliminate the need to write constructors for a class. (correct answer)
3. Common tasks can be encapsulated in methods, which facilitates code reuse throughout a program.
4. Debugging is simplified because functionality is isolated into smaller, testable units.

Question 14

1. public boolean addToCart(){ if(stockQuantity<=0) return false; stockQuantity--; return true; } (correct answer)
2. public void addToCart(){ stockQuantity++; }
3. private boolean addToCart(){ stockQuantity--; return true; }
4. public int addToCart(){ stockQuantity--; return stockQuantity; }

Question 15

1. All fields private with getter methods for ID and name, and a single setter method for all fields
2. ID field private with only a getter method, name field private with getter and setter methods, GPA field private with getter and updateGPA method (correct answer)
3. All fields public to allow maximum flexibility for different use cases and future requirements
4. ID field protected with getter method, name and GPA fields public with validation in setter methods

Question 16

1. Store temperature in Celsius as a public field and provide conversion methods that return calculated values
2. Store temperature in the format of the first value set and provide conversion methods based on stored format
3. Store temperature in Kelvin internally with public methods for setting/getting in Celsius or Fahrenheit, validating against absolute zero (correct answer)
4. Store temperature in both Celsius and Fahrenheit fields to avoid repeated calculations and provide direct access methods

Question 17

1. Use a single ArrayList with public search methods that iterate through all books
2. Use multiple HashMap collections with public methods that expose the maps for searching
3. Use multiple private HashMap collections with public search methods returning Book copies (correct answer)
4. Use a single HashMap<String, Book> with public methods returning internal references

Question 18

1. Whether the internal time representation uses 12-hour or 24-hour format
2. Whether the class provides both 12-hour and 24-hour display formats
3. Whether the time is stored as separate hour/minute fields or total minutes since midnight
4. Whether minute and hour overflow is handled internally or delegated to client code (correct answer)

Question 19

public void addItem(Item item) {
    items.add(item);
    totalPrice += item.getPrice();
}

public void removeItem(Item item) {
    if (items.remove(item)) {
        totalPrice -= item.getPrice();
    }
}

1. Remove the totalPrice field and calculate the total dynamically from the items list (correct answer)
2. Make totalPrice public so clients can verify the calculation is correct
3. Add a recalculateTotal() method that clients can call to ensure accuracy
4. Store prices separately in a parallel ArrayList to improve calculation efficiency

Question 20

1. Make the balance field public and rely on client code to check the balance before making withdrawals
2. Use a private balance field with public getter and setter methods, where the setter validates non-negative values
3. Use a private balance field with a public getter method and separate deposit/withdraw methods that validate operations (correct answer)
4. Use a protected balance field with public methods that document the requirement but don't enforce validation