Unit 8

Question 1

What is a data structure?

A) A specific algorithm to process data.
B) A collection of data organized in some fashion, providing operations like insert, remove, sort, and find.
C) A type of database used for data analytics.
D) A low-level system operation on data.

Answer 1

B) A collection of data organized in some fashion, providing operations like insert, remove, sort, and find.

Question 2

Which of the following is NOT a typical operation provided by data structures?

A) Compile
B) Insert
C) Sort
D) Find

Answer 2

A) Compile

Question 3

Which of the following is an example of a data structure provided by Java?

A) String
B) ArrayList
C) int
D) println()

Answer 3

B) ArrayList

Question 4

What is true about the Java Collections Framework?

A) It includes only List and Set interfaces.
B) It is used to handle special types of data like timestamps.
C) It provides high-performance, high-quality implementations of useful data structures and algorithms.
D) Maps extend java.util.Collection.

Answer 4

C) It provides high-performance, high-quality implementations of useful data structures and algorithms.

Question 5

What is a List in Java?

A) A collection of key-value pairs.
B) An ordered collection of elements accessed by integer indexes.
C) A set of unique elements without duplicates.
D) A method to handle exceptions.

Answer 5

B) An ordered collection of elements accessed by integer indexes.

Question 6

What distinguishes a Map in Java?

A) Allows duplicate keys.
B) Ordered collection of key-value pairs.
C) Does not allow the retrieval of elements.
D) A collection of key-value pairs where each key uniquely maps to a value.

Answer 6

D) A collection of key-value pairs where each key uniquely maps to a value.

Question 7

What is the primary benefit of using generics in Java?

A) To allow the same method to operate on different types of collections.
B) To prevent runtime errors by enforcing type safety at compile time.
C) To increase the runtime efficiency of applications.
D) To provide cryptography capabilities to Java applications.

Answer 7

B) To prevent runtime errors by enforcing type safety at compile time.

Question 8

What will the following Java code output? List<String> list = new ArrayList<>(); list.add("hello"); list.add("world"); System.out.println(list.get(0));</String>

A) hello
B) world
C) [hello, world]
D) 0

Answer 8

A) hello

Question 9

Which interface does not allow duplicate elements?

A) List
B) Set
C) Map
D) Both List and Map

Answer 9

B) Set

Question 10

What will happen if you try to add a duplicate element to a Set in Java?

A) Compile-time error.
B) Runtime exception.
C) The duplicate element will be ignored.
D) The original element will be replaced.

Answer 10

C) The duplicate element will be ignored.

Question 11

What is wrong with this code snippet? Map map = new HashMap(); map.put(“key”, “value”); System.out.println(map.get(“value”));

A) “map” should be declared with specific types.
B) HashMap does not support the get method.
C) The get method is being called with the wrong parameter.
D) There is no error in the code.

Answer 11

C) The get method is being called with the wrong parameter.

Question 12

In Java, which collection type should be used when you need to access elements frequently by an index?

A) Set
B) Queue
C) List
D) Map

Answer 12

C) List

Question 13

What does the retainAll method do when called on a collection?

A) Removes all elements of the collection.
B) Retains only the elements in the collection that are contained in the specified collection.
C) Adds all elements from the specified collection to the collection.
D) None of the above.

Answer 13

B) Retains only the elements in the collection that are contained in the specified collection.

Question 14

Consider the following code: Set<Integer> set = new HashSet<>(); set.add(1); set.add(2); set.add(1); System.out.println(set.size()); What will it output?</Integer>

A) 2
B) 3
C) 1
D) 4

Answer 14

A) 2

Question 15

What is the primary difference between HashSet and TreeSet in Java?

A) HashSet allows null values, whereas TreeSet does not.
B) HashSet does not guarantee any order, while TreeSet stores elements in a sorted order.
C) There are no differences; they function identically.
D) TreeSet is faster than HashSet.

Answer 15

B) HashSet does not guarantee any order, while TreeSet stores elements in a sorted order.

Question 16

What is the use of the keySet method in the Map interface?

A) It returns a collection of the values in the map.
B) It checks if a particular key exists in the map.
C) It returns a Set view of the keys contained in the map.
D) It removes a key from the map.

Answer 16

C) It returns a Set view of the keys contained in the map.

Question 17

What will be the result of this Java code? List<String> list = new ArrayList<>(); list.add("A"); list.add("B"); list.remove(0); System.out.println(list.get(0));</String>

A) A
B) B
C) An IndexOutOfBoundsException
D) null

Answer 17

B) B

Question 18

What does the Collections.sort() method do?

A) Sorts any type of collection.
B) Sorts elements of a List according to natural ordering or by a provided Comparator.
C) Returns a sorted collection without modifying the original.
D) Sorts a Map by its keys.

Answer 18

B) Sorts elements of a List according to natural ordering or by a provided Comparator.

Question 19

Why are generics important in the context of the Java Collections Framework?

A) They allow Java collections to be type-safe.
B) They make Java collections run faster.
C) They are required to use Java collections.
D) They allow collections to change size dynamically.

Answer 19

A) They allow Java collections to be type-safe.

Question 20

Why might you choose LinkedList over ArrayList in Java?
A) If frequent random access to elements is needed.
B) If memory usage is the primary concern.
C) If frequent insertion and deletion of elements are needed.
D) If only sequential access of elements is required.

Answer 20

C) If frequent insertion and deletion of elements are needed.

Question 21

What operation would you use to find common elements between two sets in Java?
A) addAll()
B) retainAll()
C) removeAll()
D) clear()

Answer 21

B) retainAll()

Question 22

What Java method would you use to iterate over both the keys and values of a Map simultaneously?
A) keySet()
B) values()
C) entrySet()
D) get()

Answer 22

C) entrySet()

Question 23

What is a benefit of using generics in Java Collections?
A) Allows collections to store different types of objects.
B) Prevents ClassCastException at runtime.
C) Increases the processing speed of the program.
D) Automatically sorts any type of collection.

Answer 23

B) Prevents ClassCastException at runtime.

Question 24

What is a key advantage of using an array-based structure like ArrayList over a link-based structure like LinkedList?
A) Faster insertion and deletion at any point in the list.
B) Less memory overhead per element.
C) Elements can be accessed in constant time.
D) Better performance with a larger size of elements.

Answer 24

C) Elements can be accessed in constant time.