Java Collections Framework 📦

This repository is created as a learning guide for the Java Collections Framework (JCF). It covers the core concepts, interfaces, classes, and common use cases to help you understand how collections work in Java.

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📌 What is the Java Collections Framework?

The Java Collections Framework is a set of classes and interfaces in Java that provide a standard way to store, manipulate, and retrieve groups of objects.

It helps you:

• Store data efficiently
• Reduce programming effort
• Improve code readability and reusability
• Use well-tested, optimized data structures

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🧩 Core Interfaces

Interface	Description
Collection	Root interface of the collection hierarchy
List	Ordered collection, allows duplicates
Set	Unordered collection, does not allow duplicates
Queue	Used for holding elements prior to processing
Deque	Double-ended queue
Map	Stores key-value pairs (not a subtype of Collection)

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📚 Common Implementations

🔹 List Implementations

• ArrayList
• LinkedList
• Vector
• Stack

🔹 Set Implementations

• HashSet
• LinkedHashSet
• TreeSet

🔹 Queue / Deque Implementations

• PriorityQueue
• ArrayDeque

🔹 Map Implementations

• HashMap
• LinkedHashMap
• TreeMap
• Hashtable

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🔄 Collection Hierarchy (Simplified)

Iterable
   └── Collection
         ├── List
         ├── Set
         └── Queue

Map (separate hierarchy)

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⚙️ Basic Operations

Common operations provided by collections:

• add()
• remove()
• contains()
• size()
• isEmpty()
• clear()
• iterator()

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🔁 Iterating Through Collections

Ways to iterate:

• Enhanced for-loop
• Iterator
• ListIterator
• forEach() method

Example:

List<String> list = new ArrayList<>();
list.add("Java");
list.add("Python");

for (String lang : list) {
    System.out.println(lang);
}

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🧠 When to Use What?

• ArrayList → Fast random access
• LinkedList → Frequent insertions/deletions
• HashSet → No duplicates, fast lookup
• TreeSet → Sorted data
• HashMap → Fast key-value access
• TreeMap → Sorted keys

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🚀 Learning Goals

• Understand collection interfaces and classes
• Know differences between List, Set, Queue, and Map
• Choose the right collection for a given problem
• Practice common operations and iteration

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📖 References

• Official Java Documentation
• Oracle Java Tutorials
• Java Programming Books & Online Resources

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✨ Author

Created for learning and practice purposes.

Happy Coding! 💻🎉