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Quizzes > High School Quizzes > Technology

AP CSA Unit 6 MCQ Practice Quiz

Sharpen your skills with engaging AP CSA MCQs

Difficulty: Moderate
Grade: Grade 12
Study OutcomesCheat Sheet
Colorful paper art promoting AP Computer Science A MCQ trivia challenge for high school students.

Which of the following is a correct declaration of an int variable in Java?
int number = 5;
int number = "5";
int number == 5;
number int = 5;
The correct syntax in Java is to declare a variable by specifying the type followed by the variable name, using the '=' operator to assign a value, and ending with a semicolon. The other options either misuse the equality operator or have incorrect ordering and type mismatches.
Which keyword is used to create a new instance of a class in Java?
instance
create
new
construct
The keyword 'new' is used to instantiate a new object in Java. The other options are not recognized keywords for object creation.
What is the correct way to print the text "Hello, World!" in Java?
println("Hello, World!");
print("Hello, World!");
System.out.println("Hello, World!");
System.out.Log("Hello, World!");
Using System.out.println with the text in double quotes is the standard method for printing a line of text in Java. The other options either lack the proper class reference or use incorrect method names.
Which of the following is the correct syntax for a single-line comment in Java?
# This is a comment
/* This is a comment */
// This is a comment
In Java, a single-line comment is denoted by // at the beginning of the comment. The /* */ syntax is reserved for multi-line comments, while the other symbols are not used for commenting in Java.
Which of the following is the correct way to assign a boolean variable in Java?
boolean isValid = 1;
boolean isValid = true;
boolean isValid = "true";
bool isValid = true;
In Java, boolean variables are declared with the keyword 'boolean' and can only be assigned the literal values true or false without quotes. The other options either use an incorrect type or assign values of an incompatible type.
Which of the following is the proper syntax to check if variable a is greater than variable b in an if statement?
if (a >> b) { ... }
if (a > b) { ... }
if a > b then { ... }
if (a >= b) { ... }
Using parentheses to enclose the condition and the '>' operator is the correct way to compare two variables in an if statement. The other options either misuse the operator or do not follow Java's syntax rules.
Which of the following for-loop declarations correctly iterates from 0 up to but not including 10?
for (int i = 1; i < 10; i++) { ... }
for (int i = 0; i < 10; i--) { ... }
for (int i = 0; i < 10; i++) { ... }
for (int i = 0; i <= 10; i++) { ... }
Option A initializes the counter at 0, checks that i is less than 10, and increments properly, which avoids including 10 in the iteration. The other options either include 10 or have logical errors that could lead to an infinite loop.
What is a potential problem when using a while loop without proper update to its controlling variable?
Infinite loop
Conditional evaluation never occurs
Runtime exception
Compilation error
Failing to update the controlling variable in a while loop may result in an infinite loop, as the condition remains true indefinitely. The other options do not accurately describe the typical consequence of this mistake.
If an array has 5 elements, what is the index of its last element in Java?
6
Depends on the array type
4
5
Java arrays use zero-based indexing, meaning that in an array of 5 elements, the indices run from 0 to 4. The other options do not reflect this indexing convention.
Which of the following statements best describes local variables in a Java method?
They are shared among all instances of the class
They are declared within a method and can only be accessed within that method
They are defined outside all methods to be used globally
They are declared inside a class and can be accessed by all methods in the class
Local variables are declared inside a method, and their scope is limited to that method only. The other options incorrectly describe instance variables or global variables, which have broader scopes.
What is the purpose of a constructor in a Java class?
To define the class methods
To initialize new objects with default or provided values
To declare instance variables
To allow inheritance between classes
A constructor in Java is a special method used to initialize new objects with specific initial states. It sets up instance variables with default or provided values, unlike other methods which serve different purposes.
What is method overloading in Java?
Writing a method that calls itself
Creating methods that perform long-running tasks
Redefining a method in a subclass with a different implementation
Defining multiple methods in the same class with the same name but different parameters
Method overloading allows a class to have multiple methods with the same name as long as their parameter lists differ. The other options describe method overriding or recursion, which are different concepts.
Which of the following keywords is used to extend a class and inherit its properties in Java?
extends
implements
inherits
super
The 'extends' keyword is used in Java to create a subclass that inherits properties and methods from a superclass. 'Implements' is used for adopting interfaces, while the other options are not used for inheritance.
Which statement best differentiates an abstract class from an interface in Java?
An interface can have concrete methods and fields, while an abstract class cannot have any implemented methods
An abstract class can have both abstract and concrete methods, while an interface can only have abstract methods (pre-Java 8).
Abstract classes support multiple inheritance
Interfaces are instantiated using the new keyword
Traditionally, abstract classes in Java can include both abstract methods (without implementation) and concrete methods (with implementation), whereas interfaces were limited to abstract methods prior to Java 8. This distinction helps in choosing the appropriate structure based on the need for method implementations.
What is the effect of declaring a method as static in Java?
The method cannot return a value
The method can only access static variables
The method belongs to the class and not to any particular instance
The method is overridden in subclasses
A static method is associated with the class itself rather than an instance of the class, meaning it can be invoked without creating an object. Although static methods have access restrictions, the key characteristic is their class-level association.
Consider a recursive method that does not have a proper base case. What is the most likely outcome when this method is executed?
The program will run forever without any error
The method will automatically switch to an iterative process
The Java compiler will catch the error at compile time
A StackOverflowError occurs due to infinite recursion
Without a proper base case, the recursive method calls itself indefinitely until the available stack memory is exhausted, resulting in a StackOverflowError. Java does not catch this at compile time, and it does not automatically convert recursion to iteration.
Which of the following best describes dynamic method dispatch in Java?
It is used to overload methods within a class
It eliminates the need for explicit casting between types
The determination of which method to call is done at compile time
The call to an overridden method is resolved at runtime based on the object's actual type
Dynamic method dispatch allows Java to determine at runtime which overridden method should be executed based on the actual type of the object. This runtime resolution is a cornerstone of polymorphism in object-oriented programming.
When catching exceptions in Java, which of the following is true regarding checked exceptions?
They are checked at runtime
They must always be subclassed from RuntimeException
They can be ignored completely
Checked exceptions must be either caught or declared in the method signature
Checked exceptions require that a method explicitly handles them either by using a try-catch block or by declaring them with the 'throws' keyword in its signature. This enforced handling distinguishes them from unchecked exceptions, which do not require such declaration.
Which of the following Big-O notations best describes the time complexity of a binary search in a sorted array?
O(1)
O(n)
O(log n)
O(n log n)
Binary search works by repeatedly dividing the search interval in half, resulting in a time complexity of O(log n). The other notations represent different complexities that do not match the efficiency of binary search.
What is the primary purpose of garbage collection in Java?
To delete files from the file system
To compile Java code into bytecode
To optimize the execution speed of Java programs
To automatically reclaim memory by removing objects that are no longer reachable
Garbage collection in Java automatically frees memory by identifying and removing objects that are no longer referenced in a program. This process helps in managing memory resources and preventing memory leaks, rather than handling file deletion or code compilation.
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Study Outcomes

  1. Analyze core object-oriented programming principles.
  2. Apply algorithmic problem-solving techniques to code scenarios.
  3. Evaluate program outputs based on given conditions and loops.
  4. Interpret syntax and semantics of Java-based code examples.
  5. Integrate debugging strategies to identify and fix errors.

AP CSA MCQ Review: Unit 6 Practice Cheat Sheet

  1. Declaring and Initializing Arrays - In Java, you can create an array with a fixed size using int[] numbers = new int[5]; or initialize it directly like String[] fruits = {"Apple", "Banana", "Cherry"};. This reserves memory and sets you up to start storing data right away. Array Basics on Fiveable
  2. Traversing with Classic Loops - Use a standard for loop to move through each element by index: for (int i = 0; i < numbers.length; i++) { /* process numbers[i] */ }. This approach gives you full control over start, end, and step values. Looping Techniques
  3. Enhanced For Loop (For-Each) - The for-each loop, for (int num : numbers) { /* process num */ }, simplifies traversal by abstracting away the index. It's perfect when you just need to read or process every element in order. For-Each Magic
  4. Common Array Algorithms - Practice writing routines like finding the maximum, calculating the average, or reversing an array. These problems build your problem‑solving muscle and show the power of arrays in action. Algorithm Warmups
  5. Zero-Based Indexing - Remember, Java arrays start at index 0, so the first element is array[0] and the last is array[array.length - 1]. This convention is super common and worth internalizing early! Index Insights
  6. Handling Out-of-Bounds Errors - An ArrayIndexOutOfBoundsException pops up if you try to access array[-1] or array[array.length]. Always double-check your loop boundaries to keep your code crash-free. Error Prevention Tips
  7. Modifying Elements - Change values on the fly by assigning new data to a given index, e.g., numbers[2] = 10;. This direct access makes arrays super efficient for updates. Update Tricks
  8. Arrays vs. ArrayLists - Arrays have a fixed size once created, whereas ArrayList<T> can grow and shrink dynamically. Choose arrays for speed and predictable memory, and ArrayLists for flexible sizing. Collection Comparison
  9. Methods with Array Parameters - Define methods that accept arrays (void process(int[] data)) or return them (int[] generate()) to promote clean, modular code. This strategy boosts reusability and keeps your main method tidy. Method Modularity
  10. Searching and Sorting - Master linear search, binary search, and fundamental sorts like selection, insertion, and merge sort. These classic algorithms are frequently tested and form the backbone of efficient data handling. Algorithm Deep Dive
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