ITSW 3173 D287 Java Frameworks

Correct Answer

B. Set, List, Queue

Explanation

The Java Collections Framework provides several core interfaces. The primary ones that extend the Collection interface are List, Set, and Queue. These interfaces define common behaviors for groups of objects and are widely used in Java programming to manage collections of elements. Map does not extend the Collection interface and operates differently, associating keys with values.

Why other options are wrong

A. Map, List, Set

This is incorrect because Map is not part of the Collection interface hierarchy. Although it is part of the Collections Framework, it uses a different structure that focuses on key-value pairs. Therefore, it cannot be grouped with the other types that extend Collection.

C. List, Stack, Array

This is incorrect because Stack is a legacy class that extends Vector and is not considered a primary collection type under the Collection interface. Additionally, Array is not part of the Collections Framework but rather a core language structure in Java, and it doesn’t implement the Collection interface.

D. Queue, Map, Stack

This is incorrect because, again, Map is not part of the Collection interface. Stack, as noted earlier, is a legacy class and not one of the main interfaces under Collection. Only Queue from this group extends the Collection interface directly.

Correct Answer

B. It ensures that elements are processed in the order they were added.

Explanation

The FIFO (First-In, First-Out) principle is fundamental to the behavior of a queue. It ensures that elements are processed in the same order they were added, meaning the first element added is the first one to be removed and processed. This order is crucial in scenarios like task scheduling, where the first task must be processed first, or in print queues, where documents are printed in the order they were sent.

Why other options are wrong

A. It allows the most recently added element to be processed first.

This is incorrect. The principle that allows the most recently added element to be processed first is known as LIFO (Last-In, First-Out), which is typical for a stack, not a queue.

C. It requires that all elements be processed simultaneously.

This is incorrect. FIFO processes elements sequentially, one at a time, based on their order of arrival. Simultaneous processing is not a characteristic of the FIFO principle.

D. It allows for random access to elements within the queue.

This is incorrect. FIFO processes elements in the order they were added and does not allow random access to elements. A queue typically follows a strict order of removal (front to back), which makes random access inappropriate for queues.

Correct Answer

C. To associate keys with values

Explanation

The Map interface in Java is designed to store key-value pairs, where each key is associated with exactly one value. It enables efficient retrieval, insertion, and deletion of elements based on the key. This makes Map ideal for scenarios requiring quick access to data using identifiers, like lookup tables.

Why other options are wrong

A. To store elements in a sorted order

This is incorrect because sorting is not the primary function of a Map. While some implementations like TreeMap do store entries in a sorted order based on keys, the core purpose of the Map interface is to associate keys with values, not to maintain order.

B. To maintain a collection of unique elements

This is incorrect because the Set interface is specifically designed for maintaining a collection of unique elements. In a Map, uniqueness is enforced only on keys, not on values. Duplicate values are allowed, so this option does not accurately describe a Map.

D. To allow duplicate entries

This is incorrect because Map does not allow duplicate keys. Although it allows duplicate values, the uniqueness of keys is a fundamental characteristic of Map. This option could be misleading and doesn't describe the primary function of a Map.

Correct Answer

A. Stack

Explanation

Depth-first search (DFS) uses a stack to explore as deeply as possible along each branch before backtracking. A stack allows the algorithm to "remember" the current path and backtrack when necessary, making it ideal for DFS traversal of graphs.

Why other options are wrong

B. Queue

This is incorrect because a queue is used in breadth-first search (BFS), where nodes are explored level by level, not deep first.

C. Priority queue

This is incorrect because a priority queue is generally used for algorithms like Dijkstra’s, where elements are processed based on priority rather than the order of exploration.

D. Tree

This is incorrect because a tree is a type of data structure used to organize data, but it’s not used to implement DFS directly. DFS is a graph traversal algorithm, and stacks are used for that.

Correct Answer

E. It allows null value to be stored.

Explanation

java.util.HashSet allows one null element to be stored. Although it does not maintain the order of the elements, it does support the insertion of a single null value. It does not keep elements in a sorted order, nor does it allow duplicates, as it is based on a hash table implementation that enforces uniqueness by using hash codes to identify and store elements.

Why other options are wrong

A. It keeps the elements in a sorted order.

This is incorrect because HashSet does not maintain any specific order of its elements. The order is unpredictable and may change if the set is modified.

B. It allows duplicate elements because it is based on HashMap.

This is incorrect. HashSet does not allow duplicate elements. It is true that HashSet is backed by a HashMap, but the uniqueness of elements is ensured by the hash values, and duplicates are not allowed.

C. It stores name-value pairs.

This is incorrect because HashSet is a collection of single elements, not key-value pairs. Key-value pairs are stored in Map implementations such as HashMap.

D. The order of elements while iteration remains the same always.

This is incorrect because the order of elements in a HashSet is not guaranteed to remain the same, and it may vary between different executions or due to modifications to the set.

Correct Answer

D. traverse the keys in sorted order

Explanation

The TreeMap class in Java is part of the java.util package and implements the Map interface. It stores key-value pairs in a red-black tree, which maintains the keys in sorted order. Thus, it is efficient for operations such as traversing the keys in sorted order.

Why other options are wrong

A. locate a value

This is incorrect because while TreeMap allows for fast lookup by key, it is not specifically designed to efficiently locate values by themselves. Its primary benefit is sorted key traversal.

B. insert a value

This is incorrect because while TreeMap does support inserting key-value pairs, insertion is not the primary operation for which it is known. The tree structure ensures sorted keys but may not be as fast for insertion as other structures like HashMap.

C. delete a value

This is incorrect because deletion of values can be done in TreeMap, but like insertion, it's not its primary strength. The sorting of keys is the most notable feature of TreeMap.

Correct Answer

D. TreeSet

Explanation

TreeSet<T> is the concrete class that implements the SortedSet interface and is designed for rapid retrieval of elements. It provides a sorted collection, meaning that elements are stored in a natural order (or according to a specified comparator). This ensures that the retrieval of elements, particularly for operations like searching, is efficient, typically with a time complexity of O(log n).

Why other options are wrong

A. Vector

This is incorrect because Vector<T> is not part of the Set interface and does not provide a sorted collection. It is a dynamic array-based implementation of the List interface.

B. LinkedList

This is incorrect because LinkedList<T> also does not implement SortedSet. It is part of the List interface and stores elements in a doubly-linked list structure, which does not guarantee any sorting of the elements.

C. HashSet

This is incorrect because HashSet<T> is an implementation of the Set interface that does not maintain any order, including sorting. It is designed for fast lookup, but it does not provide a sorted structure like TreeSet.

Correct Answer

A. A Vector is a synchronized dynamic array that can grow in size.

Explanation

A Vector is a synchronized implementation of a dynamic array in the Java Collections Framework. It automatically grows in size when more elements are added beyond its initial capacity. Its synchronization makes it thread-safe, but this can lead to performance drawbacks when compared to other collections, such as ArrayList, which are not synchronized. A Vector is part of the legacy collection classes and is less commonly used today in favor of newer, more efficient collections.

Why other options are wrong

B. A Vector is a type of Map that stores key-value pairs.

This statement is incorrect because a Vector is a type of List, not a Map. A Map is used to store key-value pairs, whereas a Vector stores a sequence of elements, like other List implementations.

C. A Vector is a collection that does not allow duplicate elements.

This is incorrect because Vector allows duplicate elements. It functions as a List, meaning it can contain multiple occurrences of the same element, unlike a Set that does not allow duplicates.

D. A Vector is an unordered collection of elements.

This statement is incorrect. While a Vector does not guarantee any specific order for its elements, it does maintain the insertion order (elements are accessed in the same order they were added), unlike some unordered collections like HashSet. Therefore, it is not "unordered."

Correct Answer

A. Lists often allow their size to be easily updated to hold as many data values as needed

Explanation

The primary benefit of using a list is that lists are dynamic in nature, and their size can be easily updated to accommodate additional data values as needed. Lists, such as ArrayList or LinkedList, can grow in size without needing to be resized manually, which is a significant advantage in programs that need to manage dynamic data.

Why other options are wrong

B. Lists convert all elements to strings so that they can be inspected character-by-character

This is incorrect. Lists do not automatically convert elements to strings, nor are they specifically designed to inspect elements character-by-character. Lists can store various types of objects, and any string manipulation would need to be done explicitly in the program.

C. Lists prevent duplicate data values from appearing in the list

This is incorrect. Lists do not prevent duplicate elements. If duplicates are not desired, a Set would be more appropriate, as it ensures uniqueness of elements.

D. Lists are used to store all input data so that there is a running record of all user input

This is incorrect. While lists can be used to store data, their primary benefit is not about maintaining a running record of user input. They simply allow the storage and manipulation of data in a sequential manner. A List does not inherently track input or act as a "record keeper."