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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