MCQs for AP Comp Sci A 2015 Exam

Concepts and Syntax

1. Which of the following is not a valid variable name in Java?
   – (a) _myVariable
   – (b) 1myVariable
   – (c) myVariable
   – (d) MyVariable

   

2. What is the output of the following Java code?
   java int x = 10; System.out.println(x++); System.out.println(x);
   – (a) 10, 11
   – (b) 11, 11
   – (c) 10, 10
   – (d) 11, 10

3. Which of the following is the correct syntax for creating an object of class MyObject in Java?
   – (a) new MyObject()
   – (b) MyObject()
   – (c) MyObject new
   – (d) new MyObject

   

4. What is the purpose of the this keyword in Java?
   – (a) To refer to the current object
   – (b) To refer to the superclass
   – (c) To refer to the instance variables
   – (d) To refer to the static methods

   

5. Which of the following is a valid method signature in Java?
   – (a) public static void myMethod(int a, String b)
   – (b) public myMethod(int a, String b)
   – (c) void public myMethod(int a, String b)
   – (d) public int myMethod(int a, String b)

Arrays and Strings

6. Which of the following is the correct way to declare a 2D array of integers in Java?
   – (a) int[][] myArray = new int[3][4];
   – (b) int myArray[][] = new int[3][4];
   – (c) int[] myArray[3][4] = new int[3][4];
   – (d) int[][] myArray = int[3][4];

7. What is the output of the following Java code?
   java String myString = "Hello World"; myString.toUpperCase(); System.out.println(myString);
   – (a) Hello World
   – (b) HELLO WORLD
   – (c) hello world
   – (d) hello_world

8. Which of the following is a valid method in the String class in Java?
   – (a) indexOf(String substring)
   – (b) charAt(int index)
   – (c) toLowerCase()
   – (d) All of the above

   

9. Which of the following is a valid way to iterate over the characters of a string in Java?
   – (a) for (char c : myString)
   – (b) for (int i = 0; i < myString.length(); i++)
   - (c) for (i in myString)
   - (d) None of the above

10. What is the purpose of the StringBuilder class in Java?
    - (a) To create a mutable string
    - (b) To create an immutable string
    - (c) To create a string with a specific capacity
    - (d) To create a string with a specific encoding

Algorithm Design and Analysis

11. Which of the following is the time complexity of the following Java code?
    java for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { System.out.println("Hello World"); } }
    - (a) O(n)
    - (b) O(n^2)
    - (c) O(n^3)
    - (d) O(n log n)

12. Which of the following is the best algorithm to use for sorting a large dataset of integers in Java?
    - (a) Bubble sort
    - (b) Selection sort
    - (c) Insertion sort
    - (d) Merge sort

13. What is the purpose of the Recursion class in Java?
    - (a) To create recursive methods
    - (b) To prevent stack overflows
    - (c) To optimize recursive calls
    - (d) None of the above

14. Which of the following is a valid way to implement a recursive method in Java?
    - (a) Recursion.myMethod()
    - (b) myMethod.recurse()
    - (c) myMethod()
    - (d) None of the above

15. What is the purpose of the try-catch block in Java?
    - (a) To handle exceptions
    - (b) To prevent errors
    - (c) To optimize code
    - (d) None of the above

Object-Oriented Programming

16. Which of the following is the correct way to define an abstract class in Java?
    - (a) abstract class MyAbstractClass { }
    - (b) class MyAbstractClass abstract { }
    - (c) MyAbstractClass abstract { }
    - (d) class MyAbstractClass { abstract; }

17. Which of the following is a valid use of the @Override annotation in Java?
    java public class MyClass extends ParentClass { @Override public void myMethod() { // Implementation } }
    - (a) To ensure that the method is overridden in the child class
    - (b) To prevent the method from being overridden in the child class
    - (c) To optimize the method in the child class
    - (d) None of the above

18. What is the purpose of the super keyword in Java?
    - (a) To refer to the superclass
    - (b) To refer to the instance variables of the superclass
    - (c) To call the constructor of the superclass
    - (d) To override the methods of the superclass

19. Which of the following is a valid way to define an interface in Java?
    - (a) interface MyInterface { }
    - (b) MyInterface interface { }
    - (c) interface MyInterface { methods; }
    - (d) class MyInterface { }

20. Which of the following is a valid way to implement an interface in Java?
    - (a) class MyClass implements MyInterface { }
    - (b) MyClass implements MyInterface { }
    - (c) implement MyInterface MyClass { }
    - (d) class MyInterface implements MyClass { }

Data Structures

21. Which of the following is the time complexity of inserting an element into a linked list?
    - (a) O(1)
    - (b) O(n)
    - (c) O(log n)
    - (d) O(n^2)

22. Which of the following is the time complexity of searching for an element in a balanced binary search tree?
    - (a) O(1)
    - (b) O(log n)
    - (c) O(n)
    - (d) O(n^2)

23. Which of the following is the best data structure to use for storing a large number of elements that need to be accessed randomly?
    - (a) Array
    - (b) Linked list
    - (c) Queue
    - (d) Stack

24. Which of the following is the best data structure to use for storing a large number of elements that need to be accessed in a FIFO (first-in, first-out) order?
    - (a) Array
    - (b) Linked list
    - (c) Queue
    - (d) Stack

25. Which of the following is the best data structure to use for storing a large number of elements that need to be accessed in a LIFO (last-in, first-out) order?
    - (a) Array
    - (b) Linked list
    - (c) Queue
    - (d) Stack

Conclusion

These are just a few examples of the types of multiple-choice questions that you may encounter on the AP Computer Science A 2015 exam. By practicing these types of questions, you can increase your chances of success on the exam.