Chapter 5: Collections Framework

The Java Collections Framework (java.util) provides a standardized architecture for representing and manipulating groups of objects. Mastering its interfaces, dynamic arrays, hash tables, balanced binary search trees, queues, and thread-safe concurrent variants is vital for building performant enterprise backend systems.

---

🧭 Subtopics & Curriculum

Click anywhere on a topic card below to open that subtopic note, or use the Obsidian button to open it directly in the Obsidian app:

Architecture & Hierarchy5.1

🗂️

5.1 Collections Framework Overview

• 1. Top-Level Hierarchy Architecture
• 2. Core Interfaces & Characteristics
• 3. Algorithmic Complexity Comparison

🔮 Open in Obsidian

Ordered Sequences5.2

📋

5.2 List Implementations

• 1. ArrayList: Dynamic Resizable Array
  • Internal Growth Policy (Java 8–21)
• 2. LinkedList: Doubly-Linked List
  • Memory Overhead & CPU Cache Locality
• 3. Vector and Stack: Legacy Synchronization

🔮 Open in Obsidian

Uniqueness & Sets5.3

🎯

5.3 Set Implementations & Uniqueness

• 1. HashSet: Internal Backing by HashMap
• 2. LinkedHashSet: Predictable Insertion Order
• 3. TreeSet: Sorted & Navigable (Red-Black Tree)

🔮 Open in Obsidian

Queues & Buffers5.4

⏳

5.4 Queue & Deque Implementations

• 1. Queue vs Deque Interface Contracts
• 2. ArrayDeque: High-Performance Resizing Circular Array
• 3. PriorityQueue: Binary Min-Heap

🔮 Open in Obsidian

Key-Value Internals5.5

🗺️

5.5 Map Hierarchy & HashMap Internals

• 1. Internal Architecture: Buckets & Treeification (Java 8+)
  • Key Internal Parameters
• 2. Hash Calculation & Index Bitmasking
• 3. LinkedHashMap & TreeMap

🔮 Open in Obsidian

Thread-Safety & Immutable5.6

⚡

5.6 Concurrent & Specialized Collections

• 1. ConcurrentHashMap: Lock-Free Reads & Fine-Grained Locking
• 2. CopyOnWriteArrayList: Thread-Safe Read-Heavy Lists
• 3. Java 9+ Immutable Factory Methods

🔮 Open in Obsidian