Java Collections Framework Quiz

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Questions and Answers

What is the purpose of the `toArray()` method in the Java Collections Framework?

It sorts the collection

It merges multiple collections

It converts a collection to an array (correct)

It reverses the collection

In the Java Collections Framework, which class provides methods to manipulate the size of a list and its elements?

`Vector`

`List`

`ArrayList` (correct)

`Set`

What is the purpose of the `Iterator` interface in the Java Collections Framework?

It enables element comparison for sorting

It provides methods for sorting a collection

It provides a way to iterate over a collection's elements (correct)

It allows for concurrent modification of collections

Which method is used to remove all elements from a collection in the Java Collections Framework?

<code>clear()</code> Signup and view all the answers

What is the purpose of the `Map.Entry` interface in the Java Collections Framework?

It represents a key-value pair in a map Signup and view all the answers

In the Java Collections Framework, which method is used to obtain a synchronized (thread-safe) version of a collection?

<code>Collections.synchronizedCollection()</code> Signup and view all the answers

What is the primary difference between a `HashSet` and a `LinkedHashSet` in the Java Collections Framework?

A <code>LinkedHashSet</code> maintains the insertion order of elements, while a <code>HashSet</code> does not Signup and view all the answers

What is the purpose of the `Collections.reverse()` method in the Java Collections Framework?

It reverses the order of elements in a list Signup and view all the answers

What will be the output of the Java code snippet that prints a HashSet containing both a Long and an Integer with the value 10?

Test - 10 Test - 10 Signup and view all the answers

What exception is thrown when two threads attempt to modify a TreeSet simultaneously?

ConcurrentModificationException is thrown Signup and view all the answers

What will be the output of the given Java program that sorts an array initialized within a loop?

12345 Signup and view all the answers

Which of these standard collection classes is NOT an implementation of the List interface?

SessionList Signup and view all the answers

What is a unique characteristic of the LinkedHashSet in Java?

It maintains the insertion order and guarantees uniqueness Signup and view all the answers

Which method is correctly used for inserting and deleting items from a queue in Java?

enqueue and dequeue Signup and view all the answers

What result does the program demonstrate when comparing two ArrayList objects for equality?

true Signup and view all the answers

What is the worst-case complexity for accessing an element in an ArrayList?

O(1) Signup and view all the answers

When executing a program using HashMap, what will be the printed output based on the provided key-value pairs?

{A=1, B=2, C=3} Signup and view all the answers

What will the output of the provided Hashtable Java code be when checking for a value that is not present?

false Signup and view all the answers

Which standard collection class provides a dynamically resizable array in Java?

ArrayList Signup and view all the answers

Which class object utilizes keys to store values in Java?

All of the mentioned Signup and view all the answers

What is the expected outcome of executing Java code that prints a Date object?

Prints Present Time & Date Signup and view all the answers

Which class objects can be utilized to create a dynamic array in Java?

ArrayList & Vector Signup and view all the answers

What is the main programming error in the Array class when trying to initialize the array?

Array not initialized with a size Signup and view all the answers

When the ArrayList 'obj2' is modified using the add method, how does this affect the equality check with 'obj1'?

The structure of 'obj2' will differ leading to inequality Signup and view all the answers

What will be the output of the Java program that uses a TreeSet to add the elements '3', '9', '1', '4', and '8'?

[1, 3, 4, 8, 9] Signup and view all the answers

In the following Java code, what will be the output? int array[] = new int; for (int i = 5; i > 0; i--) array[5-i] = i; Arrays.fill(array, 1, 4, 8);

58881 Signup and view all the answers

What will be the output of this code after clearing a Hashtable? Hashtable obj = new Hashtable(); obj.put('A', new Integer(3)); obj.put('B', new Integer(2)); obj.clear(); System.out.print(obj.size());

0 Signup and view all the answers

Which method is utilized to retrieve elements from a Properties object at a specific location?

getProperty() Signup and view all the answers

Which method is appropriate for adding an element with a corresponding key to a map in Java?

put() Signup and view all the answers

What is the proper way to remove duplicates from a List in Java?

HashSet listToSet = new HashSet(duplicateList); Signup and view all the answers

What will be the output of the provided Java program that initializes an array and sorts it?

12345 Signup and view all the answers

Which iterator is specifically designed for use with List collections in Java?

ListIterator Signup and view all the answers

Which method is used to move to the next element in a collection iterator?

next() Signup and view all the answers

Is a HashMap considered an ordered collection in Java?

False Signup and view all the answers

What will be the output of the Java program that removes the first element from a LinkedList after adding 'A', 'B', and 'C'?

[B, C] Signup and view all the answers

What does the output of the provided Java Vector program returning obj.isEmpty() indicate after all elements are removed?

true Signup and view all the answers

What will the output be after removing an entry from a Hashtable that contains keys A, B, and C?

{C=8, B=2} Signup and view all the answers

Which of the following classes implements the Set interface in Java?

HashSet Signup and view all the answers

Which interface listed is not part of Java's collection framework?

SortedList Signup and view all the answers

Which method is used to set all elements of an array to a specified value in Java?

fill() Signup and view all the answers

What will be the output of the program that tries to store elements in the Properties object and retrieves keys?

[AB, BC, CD] Signup and view all the answers

Which of the following classes does not implement the Map interface?

Vector Signup and view all the answers

Which method would you use to retrieve an element from a BitSet at a specific index?

get() Signup and view all the answers

Which exception is thrown when attempting to remove an element from a collection that is not in the proper state?

IllegalStateException Signup and view all the answers

What is the method of the HashSet class that allows you to add a new element?

add() Signup and view all the answers

Given a sorted array, what will be the result of a binary search for the number 4 in this array if the array contains numbers 1, 2, 3, 5?

3 Signup and view all the answers

What will be the output of the ArrayList program after ensuring capacity and trimming to size?

2 Signup and view all the answers

Which interface guarantees that all elements are unique?

Set Signup and view all the answers

Study Notes

Java Collections Framework Questions and Answers

Q:-1 What is the purpose of the Collections Framework?
- To provide a unified architecture for representing and manipulating collections.
Q:-2 Which interface in the Java Collections Framework represents an ordered collection of elements that can contain duplicate values?
- List
Q:-3 What is the primary difference between a List and a Set in the Java Collections Framework?
- A Set does not allow duplicate elements, while a List does.
Q:-4 Which class is typically used to implement a List in the Java Collections Framework?
- ArrayList
Q:-5 In the Java Collections Framework, which interface extends the List interface to provide more efficient insertions and deletions in the middle of the list?
- Deque
Q:-6 What is the purpose of the Map interface in the Java Collections Framework?
- To store key-value pairs.
Q:-7 Which class is typically used to implement a Map in the Java Collections Framework?
- HashMap
Q:-8 What is the primary difference between a HashMap and a TreeMap in the Java Collections Framework?
- HashMap does not maintain order, while a TreeMap does.
Q:-9 In the Java Collections Framework, which interface represents a collection of unique elements with no duplicates?
- Set
Q:-10 Which class is typically used to implement a Set in the Java Collections Framework?
- HashSet
Q:-11 What is the primary difference between a HashSet and a LinkedHashSet in the Java Collections Framework?
- LinkedHashSet maintains insertion order, while HashSet does not.
Q:-12 Which interface in the Java Collections Framework represents a collection of elements with no specific order?
- Set
Q:-13 What is the primary difference between a Queue and a Deque in the Java Collections Framework?
- A queue is a single-ended queue while a Deque is a double-ended queue.
Q:-14 Which class is typically used to implement a Deque in the Java Collections Framework?
- ArrayDeque
Q:-15 In the Java Collections Framework, which class allows you to create a synchronized (thread-safe) collection?
- Collections
Q:-16 Which interface in the Java Collections Framework extends the Set interface and represents a collection of elements stored in a sorted order?
- SortedSet
Q:-17 What is the purpose of the Comparator interface in Java Collections Framework?
- It defines a comparison function for ordering elements.
Q:-18 Which class is typically used to implement a SortedSet in the Java Collections Framework?
- TreeSet
Q:-19 In the Java Collections Framework, which interface represents a last-in, first-out (LIFO) stack of elements?
- Stack
Q:-20 What is the primary difference between a Stack and a Queue in the Java Collections Framework?
- Stack uses LIFO (Last-In-First-Out) order, while Queue uses FIFO (First-In-First-Out) order.
And so on... (The questions and answers continue in a similar format from the provided text.)

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Test your knowledge on the Java Collections Framework with this quiz. Questions cover various concepts such as the toArray() method, Iterator interface, and differences between collection classes like HashSet and LinkedHashSet. Perfect for Java developers looking to refresh their understanding of collection manipulation.

Java Collections Framework Quiz

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Podcast

Questions and Answers

What is the purpose of the toArray() method in the Java Collections Framework?

In the Java Collections Framework, which class provides methods to manipulate the size of a list and its elements?

What is the purpose of the Iterator interface in the Java Collections Framework?

Which method is used to remove all elements from a collection in the Java Collections Framework?

What is the purpose of the Map.Entry interface in the Java Collections Framework?

In the Java Collections Framework, which method is used to obtain a synchronized (thread-safe) version of a collection?

What is the primary difference between a HashSet and a LinkedHashSet in the Java Collections Framework?

What is the purpose of the Collections.reverse() method in the Java Collections Framework?

What will be the output of the Java code snippet that prints a HashSet containing both a Long and an Integer with the value 10?

What exception is thrown when two threads attempt to modify a TreeSet simultaneously?

What will be the output of the given Java program that sorts an array initialized within a loop?

Which of these standard collection classes is NOT an implementation of the List interface?

What is a unique characteristic of the LinkedHashSet in Java?

Which method is correctly used for inserting and deleting items from a queue in Java?

What result does the program demonstrate when comparing two ArrayList objects for equality?

What is the worst-case complexity for accessing an element in an ArrayList?

When executing a program using HashMap, what will be the printed output based on the provided key-value pairs?

What will the output of the provided Hashtable Java code be when checking for a value that is not present?

Which standard collection class provides a dynamically resizable array in Java?

Which class object utilizes keys to store values in Java?

What is the expected outcome of executing Java code that prints a Date object?

Which class objects can be utilized to create a dynamic array in Java?

What is the main programming error in the Array class when trying to initialize the array?

When the ArrayList 'obj2' is modified using the add method, how does this affect the equality check with 'obj1'?

What will be the output of the Java program that uses a TreeSet to add the elements '3', '9', '1', '4', and '8'?

In the following Java code, what will be the output? int array[] = new int; for (int i = 5; i > 0; i--) array[5-i] = i; Arrays.fill(array, 1, 4, 8);

What will be the output of this code after clearing a Hashtable? Hashtable obj = new Hashtable(); obj.put('A', new Integer(3)); obj.put('B', new Integer(2)); obj.clear(); System.out.print(obj.size());

Which method is utilized to retrieve elements from a Properties object at a specific location?

Which method is appropriate for adding an element with a corresponding key to a map in Java?

What is the proper way to remove duplicates from a List in Java?

What will be the output of the provided Java program that initializes an array and sorts it?

Which iterator is specifically designed for use with List collections in Java?

Which method is used to move to the next element in a collection iterator?

Is a HashMap considered an ordered collection in Java?

What will be the output of the Java program that removes the first element from a LinkedList after adding 'A', 'B', and 'C'?

What does the output of the provided Java Vector program returning obj.isEmpty() indicate after all elements are removed?

What will the output be after removing an entry from a Hashtable that contains keys A, B, and C?

Which of the following classes implements the Set interface in Java?

Which interface listed is not part of Java's collection framework?

Which method is used to set all elements of an array to a specified value in Java?

What will be the output of the program that tries to store elements in the Properties object and retrieves keys?

Which of the following classes does not implement the Map interface?

Which method would you use to retrieve an element from a BitSet at a specific index?

Which exception is thrown when attempting to remove an element from a collection that is not in the proper state?

What is the method of the HashSet class that allows you to add a new element?

Given a sorted array, what will be the result of a binary search for the number 4 in this array if the array contains numbers 1, 2, 3, 5?

What will be the output of the ArrayList program after ensuring capacity and trimming to size?

Which interface guarantees that all elements are unique?

Study Notes

Java Collections Framework Questions and Answers

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Java Collections Framework Quiz

What is the purpose of the `toArray()` method in the Java Collections Framework?

What is the purpose of the `Iterator` interface in the Java Collections Framework?

What is the purpose of the `Map.Entry` interface in the Java Collections Framework?

What is the primary difference between a `HashSet` and a `LinkedHashSet` in the Java Collections Framework?

What is the purpose of the `Collections.reverse()` method in the Java Collections Framework?