Unit2B

Question 1

1. What is encapsulation in object-oriented programming?
   
   • a) The act of inheriting methods from a parent class.
   • b) Grouping related ideas into a single unit referred to by one name.
   • c) The ability of different classes to implement the same interface.
   • d) The process of transforming an object into a string representation.

Answer 1

b) Grouping related ideas into a single unit referred to by one name.

Question 2

2. When a message is sent to an object to perform an operation, what is this action also known as?
   
   • a) Compiling
   • b) Instantiating
   • c) Invoking the method
   • d) Encapsulating the behavior

Answer 2

c) Invoking the method.

Question 3

3. What is the purpose of the this keyword in a Java class?
   
   • a) To refer to the current class’s superclass.
   • b) To refer to the current instance of the class.
   • c) To create a static reference to the class.
   • d) To call a static method of the class.

Answer 3

b) To refer to the current instance of the class.

Question 4

4. In UML, what is the standard format for documenting an attribute?
   
   • a) attributeName: Type
   • b) Type attributeName
   • c) attributeName()
   • d) Type: attributeName

Answer 4

a) attributeName: Type

Question 5

5. When creating a new object in Java using a constructor with parameters, what are these parameters used for?
   
   • a) To set static fields of the class.
   • b) To initialize the object’s state with specific values.
   • c) To determine the number of objects to create.
   • d) To call the superclass’s constructor.

Answer 5

b) To initialize the object’s state with specific values.

Question 6

6. What is the output when you instantiate a Dog object with the name “Rusty”, color “red”, and then call dog.getName() if getName() is an accessor method?
   
   • a) “Rusty”
   • b) “red”
   • c) “Dog”
   • d) There will be a compilation error.

Answer 6

a) “Rusty”

Question 7

7. What is the primary role of the main method in a Java class?
   
   • a) To declare variables
   • b) To act as the entry point of the program
   • c) To define constants
   • d) To allocate memory for objects

Answer 7

b) To act as the entry point of the program.

Question 8

8. What would be a result of setting one object reference equal to another, e.g., object1 = object2;?
   
   • a) object1 will be a copy of object2.
   • b) object1 will refer to a new instance of the class.
   • c) object1 will refer to the same memory location as object2.
   • d) object2 will be set to null.

Answer 8

c) object1 will refer to the same memory location as object2.

Question 9

9. How does an ArrayList differ from a standard array in Java?
   
   • a) An ArrayList can only store objects, not primitive types.
   • b) An ArrayList cannot be iterated over with a for-each loop.
   • c) An ArrayList’s size can dynamically change.
   • d) An ArrayList requires elements to be of the same type.

Answer 9

c) An ArrayList’s size can dynamically change.

Question 10

10. If an object is perfectly designed and highly reusable, into which domain is it most likely to fit?
    
    • a) Foundation domain
    • b) Architecture domain
    • c) Business domain
    • d) Application domain

Answer 10

a) Foundation domain.

Question 11

11. Which of these classes would be considered more reusable?
    
    • a) A class with attributes specific to a frequent-flyer program.
    • b) A class with general attributes like name and address.

Answer 11

b) A class with general attributes like name and address.

Question 12

12. What is the correct way to declare and instantiate an ArrayList of String in Java?
    
    • a) ArrayList<String> myList = new ArrayList<String>();
    • b) String[] myList = new ArrayList();
    • c) ArrayList myList = new String[10];
    • d) ArrayList<String> myList = new String[10];

Answer 12

a) ArrayList<String> myList = new ArrayList<String>();</String></String>

Question 13

13. Which operation on an array can potentially throw an ArrayIndexOutOfBoundsException in Java?
    
    • a) Accessing an element at a negative index.
    • b) Accessing an element beyond the end of the array.
    • c) Assigning a value to an array element within the array’s bounds.
    • d) Declaring an array with a specific size.

Answer 13

b) Accessing an element beyond the end of the array.

Question 14

14. What is the main disadvantage of using arrays over ArrayList when it comes to adding or removing elements?
    
    • a) Arrays are immutable.
    • b) Arrays do not have built-in methods to add or remove elements.
    • c) Arrays can only hold primitive type

Answer 14

b) Arrays do not have built-in methods to add or remove elements.

Question 15

• Which one of the following statements about object references in Java is true?
  
  • a) When you assign one reference variable to another, both refer to separate objects in memory.
  • b) When you assign one reference variable to another, they both refer to the same object in memory.
  • c) Reference variables can be used interchangeably with primitive types.
  • d) Reference variables can point to null, which means they are associated with a valid object instance.

Answer 15

b) When you assign one reference variable to another, they both refer to the same object in memory.

Question 16

• If a method in Java is named as printStudentDetails and it prints out the student’s name and ID, what kind of method is it?
  
  • a) Accessor
  • b) Mutator
  • c) Constructor
  • d) None of the above

Answer 16

d) None of the above - It’s likely a method for displaying or printing information rather than getting or setting it.

Question 17

• What does the ArrayList method remove(int index) do?
  
  • a) It adds an element at the specified index.
  • b) It returns the element at the specified index without removing it.
  • c) It removes the element at the specified index.
  • d) It checks if an element exists at the specified index.

Answer 17

c) It removes the element at the specified index.

Question 18

• What is the purpose of a constructor in a Java class?
  
  • a) To destroy an object when it’s no longer needed.
  • b) To initialize a new object with default or given values.
  • c) To set static fields of the class.
  • d) To act as a getter method for private fields.

Answer 18

b) To initialize a new object with default or given values.

Question 19

• What principle allows a single variable name to refer to objects of multiple types that are related by some class hierarchy?
  
  • a) Encapsulation
  • b) Inheritance
  • c) Polymorphism
  • d) Composition

Answer 19

c) Polymorphism

Question 20

• In the Dog class example from the slides, what will be the output of calling dog321.chase("cat", 5, 20); assuming chase method is properly implemented to print the chase action?
  
  • a) “Dog is chasing cat at speed 5 for 20 meters.”
  • b) “Dog is not chasing.”
  • c) No output, as the method does not print anything.
  • d) The actual output depends on the implementation of the chase method in the Dog class.

Answer 20

d) The actual output depends on the implementation of the chase method in the Dog class.