What are Java Collections Framework classes

💡 Concept: Java Collections Framework

The Java Collections Framework (JCF) provides a set of interfaces and classes to store and manipulate groups of objects efficiently.

📘 Quick Intro

It includes core interfaces like List, Set, Map, and Queue, with multiple concrete implementations.

🧠 Analogy

Think of JCF as a toolbox where each tool is designed for different storage and retrieval tasks.

🔧 Technical Explanation

List: Ordered collection with duplicates allowed (ArrayList, LinkedList).
Set: Collection with no duplicates (HashSet, TreeSet).
Map: Key-value pairs (HashMap, TreeMap).
Queue: FIFO data structure (PriorityQueue, LinkedList).
Provides algorithms like sorting, searching, and synchronization wrappers.

🎯 Use Cases

✅ Manage collections of objects.
✅ Efficient data retrieval and manipulation.
✅ Support for concurrency-safe collections.

💻 Example Using Java Collections Framework


import java.util.*;

public class Example {
    public static void main(String[] args) {
        List list = new ArrayList<>();
        list.add("Java");
        list.add("Collections");
        list.add("Framework");
        System.out.println(list);
    }
}

❓ Interview Q&A

Q1: What is the Java Collections Framework?
A: A set of interfaces and classes for data structures.

Q2: Name core interfaces in JCF.
A: List, Set, Map, Queue.

Q3: What implementations does List have?
A: ArrayList, LinkedList.

Q4: Difference between Set and List?
A: Set has no duplicates; List allows duplicates.

Q5: What is a Map?
A: Key-value pairs collection.

Q6: Can JCF be synchronized?
A: Yes, via wrappers.

Q7: What is Queue used for?
A: FIFO data structure.

Q8: Name some Set implementations.
A: HashSet, TreeSet.

Q9: What is Collections class?
A: Utility class with algorithms.

Q10: Difference between ArrayList and LinkedList?
A: ArrayList uses array; LinkedList uses nodes.

📝 MCQs

Q1. What is Java Collections Framework?

Set of algorithms
Set of interfaces and classes for data structures
A language
None

Q2. Name core interfaces in JCF

Runnable, Thread
List, Set, Map, Queue
Object, Class
None

Q3. What implementations does List have?

HashMap, TreeMap
ArrayList, LinkedList
Set, Map
Queue, Stack

Q4. Difference between Set and List?

Both allow duplicates
Set no duplicates; List allows duplicates
List no duplicates
None

Q5. What is a Map?

List
Set
Key-value pairs collection
Queue

Q6. Can JCF be synchronized?

No
Yes, via wrappers
Only in Java 9+
Sometimes

Q7. What is Queue used for?

LIFO
FIFO data structure
Random access
None

Q8. Name some Set implementations

HashMap, TreeMap
HashSet, TreeSet
ArrayList, LinkedList
Queue, Stack

Q9. What is Collections class?

Interface
Class
Utility class with algorithms
Abstract class

Q10. Difference between ArrayList and LinkedList?

Both use arrays
ArrayList uses array; LinkedList uses nodes
Both use nodes
None

💡 Bonus Insight

The Java Collections Framework is foundational for efficient data management in Java applications.

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