Java - Java Collections Framework (JCF)
1️⃣ What is the Java Collections Framework?
The Java Collections Framework is a set of classes and interfaces in Java that help you store, organize, and manage groups of objects efficiently.
Instead of using simple arrays (which have fixed size and limited features), collections provide flexible and powerful ways to work with data.
Think of it as a ready-made toolkit for handling data structures like lists, sets, and maps.
2️⃣ Why do we use Collections?
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Arrays have fixed size — collections can grow or shrink
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Built-in methods for sorting, searching, inserting, deleting
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Improves code readability and reuse
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Saves time because structures are already implemented
Example: Instead of manually writing logic to resize arrays, you can use ArrayList.
3️⃣ Main Parts of the Framework
The framework mainly consists of:
✅ Interfaces (Blueprints)
They define how collections should behave:
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List → Ordered collection (duplicates allowed)
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Set → Unique elements only
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Queue → Elements processed in order (FIFO)
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Map → Key–value pairs
✅ Classes (Implementations)
Actual working versions of those interfaces:
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ArrayList,LinkedList→ implement List -
HashSet,TreeSet→ implement Set -
PriorityQueue→ implements Queue -
HashMap,TreeMap→ implement Map
✅ Algorithms & Utilities
Java provides helper methods for:
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Sorting
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Searching
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Reversing
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Shuffling
These are available through the Collections utility class.