AP CSA Code HS section 2 Questions and Answers (Passed with 100%)

AP CSA Code HS section 2 Questions and Answers (Passed with 100%) What is an object in Java? An object is something that contains both state and behavior. Which of the following best describes the relationship between a class and an object? A class definition specifies the attributes and behavior of every object that will be made. Every class definition has each of the following EXCEPT A name Defined attributes Defined behaviors to manipulate the state of the objects Defined objects as copies of the class Defined objects as copies of the class Consider this class definition of a Pineapple. public class Pineapple { private boolean isRipe; private String color; private double weight; // Rest of class goes here } When we use this class to create Pineapple objects, which of the following is guaranteed to be true? Every Pineapple object will have the same attributes. What is a constructor in Java? A constructor allows us to create a new instance of a class, usually initializing instance variables. Refer to the Card class shown below. public class Card { private String suit; private int value; //13 values for each suit in deck (0 to 12) public Card (String cardSuit, int cardValue) { /* implementation */} // Rest of the class goes here } Which of the following is the correct /* implementation */ code for the constructor in the Card class? suit = cardSuit; value = cardValue; public class Shark { // Attributes private String habitat; private int age; public Shark(String region, int sharkAge) { habitat = region; age = sharkAge; } } Which of the following choices is a formal parameter of the constructor? sharkAge What is the purpose of overloading a class' constructor? It allows the user to set the values of different combinations of the instance variables when the object is created. Which of the following is NOT part of the constructor signature? Which instance variables are initialized Which of the following is NOT a valid way to overload this constructor? For brevity, only the signature is given. Pineapple Pineapple(String color) a. Pineapple Pineapple() b. Pineapple Pineapple(String color, int age) c. Pineapple Pineapple(int age, String species) d. Pineapple FancyPineapple(String color, int age) Pineapple FancyPineapple(String color, int age) What is the importance of the null value? null allows a reference variable to be empty and not hold any memory address. A reference variable holds a special value. What is this special value? The memory address of an object Consider this code snippet that uses a class called Rectangle. int roomHeight = 40; int roomWidth = roomHeight * 3; Rectangle room = new Rectangle(roomHeight, roomWidth); Which of the following is a reference variable? room roomHeight roomWidth Rectangle room What does it mean to be a client of a class? Being a client of a class means that we can use its methods and functionality without necessarily understanding how it works. Suppose a program is a client of the Player class. Here is a snippet of code contained in the program Player firstPlayer = new Player("Karel", "Warrior", "Mote Prime", 90); Looking at the documentation of the class, you find the signature for the constructor, shown below. Player Player(String name, String role, String location, int health); Where would you find the formal parameters? In the program. In the documentation. In the library. Both the program and the documentation contain formal parameters. In the documentation. You are using a class as a client. What would you need to know in order to create an object of the class you intend to use? You need to know the formal parameters in order to pass in actual parameters. What is an instance method? An instance method is a piece of code called on a specific instance (an object) of the class. It is called with a receiver object. Which of the following is a correctly written method for the class below? public class Timer { private int startMin; private int length; public Timer(int minute, int duration) { startMin = minute; length = duration; }