My Custom Java Collections Library

A personal project to build core Java data structures from scratch, to deeply understand DSA and Java internals.

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Purpose

This library re-implements popular collections like arrays, ArrayList, LinkedList, Stack, Queue, HashMap, Set, Tree, Heap, and more — from scratch. It’s designed for learning, practicing clean code, and building stuff.

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Phase 0 — Raw Arrays

✅ RawIntArray

• add(value)
• addAt(index, value)
• removeAt(index)
• remove(value)
• find(value)
• findBinary(value)
• indexOf(value)
• contains(value)
• get(index)
• set(index, value)
• len()
• isEmpty()
• clear()
• display()
• bubbleSort()
• selectionSort()
• insertionSort()
• max()
• Unit Tests ✅

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Phase 1 — Lists

✅ MyArrayList

• add(value)
• display()
• addAt(index, value)
• removeAt(index)
• remove(value)
• removeAll(value)
• find(value)
• indexOf(value)
• contains(value)
• get(index)
• set(index, value)
• size()
• isEmpty()
• clear()
• toArray()
• iterator()

✅ MyLinkedList

• add(value)
• addFirst(value)
• addLast(value)
• remove(value)
• removeFirst()
• removeLast()
• find(value)
• indexOf(value)
• contains(value)
• get(index)
• set(index, value)
• count()
• isEmpty()
• clear()
• iterator()

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Phase 2 — Linear Structures

✅ MyStack

• push(value)
• pop()
• peek()
• isEmpty()
• count()
• clear()

✅ MyQueue

• enqueue(value)
• dequeue()
• peek()
• isEmpty()
• count()
• clear()

✅ MyDeque

• addFirst(value)
• addLast(value)
• removeFirst()
• removeLast()
• peekFirst()
• peekLast()
• isEmpty()
• count()
• clear()

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Phase 3 — Map & Set

✅ MyHashMap<K,V>

• add(key, value)
• get(key)
• remove(key)
• containsKey(key)
• containsValue(value)
• keys()
• values()
• count()
• isEmpty()
• clear()

✅ MyHashSet

• add(value)
• remove(value)
• contains(value)
• count()
• isEmpty()
• clear()

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Phase 4 — Trees & Heaps

✅ MyBinarySearchTree

• add(value)
• remove(value)
• find(value)
• contains(value)
• traverseInOrder()
• traversePreOrder()
• traversePostOrder()
• getMin()
• getMax()
• count()
• isEmpty()
• clear()

✅ MyPriorityQueue (Heap)

• add(value)
• poll()
• peek()
• isEmpty()
• count()
• clear()

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Phase 5 — Infrastructure

• Make all collections generic <T> or <K,V>
• Implement Iterable<T> where needed
• Add proper exceptions (IndexOutOfBoundsException, etc.)
• Add JUnit tests for all
• Add JavaDocs for all classes & methods
• Make nice CLI banner (✅ already started!)
• Example main() for each structure

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✨ Future Ideas

• AVL Tree or Red-Black Tree
• LRU Cache
• Thread-safe collections
• Serialization support
• Publish as a Maven/Gradle artifact
• Performance benchmarks vs. java.util

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💡 How to Use

Clone the repo and run your CLI banner:

javac -d out src/**/*.java
java MyCollectionsApp

📜 License

This project is licensed under the MIT License — see the LICENSE file for details.

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✍️ Author

Ayoub El-mahjouby GitHub Profile