Java

Collections Overview

Arrays are limited. Meet the Collections Framework: flexible groups of objects.

By TechCoder TeamLast updated: 2026-06-02
In a Nutshell

Arrays are limited. Meet the Collections Framework: flexible groups of objects. This hands-on tutorial focuses on practical implementation of collections overview concepts.

Collections Framework

The Collections Framework is a unified architecture for representing and manipulating collections (groups of objects).

It provides ready-made data structures like Lists, Sets, and Maps.

Why Collections?

Arrays have a fixed size. Collections can grow and shrink dynamically.

The Hierarchy

  • Iterable (Interface)

    • Collection (Interface)
      • List (Order preserved, Duplicates allowed)
        • ArrayList
        • LinkedList
        • Vector
      • Set (Unordered, Unique elements)
        • HashSet
        • LinkedHashSet (Ordered)
        • TreeSet (Sorted)
      • Queue (FIFO: First In First Out)
        • PriorityQueue

  • Map (Key-Value pairs) - Not a subtype of Collection interface

    • HashMap
    • LinkedHashMap
    • TreeMap

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Quiz

Quiz

Question 1 of 3

Which of these allows duplicate elements?

Set
List
Map Keys

Next Steps

Let's dive into the most specific type: Lists.