Learn why the Map interface in Java is not part of the Collection hierarchy. Understand the design reasoning, key differences, and how it benefits the Java Collection Framework.

Ramesh Fadatare

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Mar 25, 2025

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🔍 Short Answer:

Because Map represents key-value pairs, while Collection represents a group of elements (values only).

➡️ They are conceptually different — that’s why Map doesn’t extend Collection.

🔎 Let’s Break It Down

The collection interfaces are divided into two groups:

The most basic interface, java.util.Collection.

The other collection interfaces are based on Map:

✅ 1. Collection is a group of elements

• It includes: List, Set, Queue, etc.
• It focuses on a single group of objects.
• Example:

List<String> names = List.of("Ramesh", "Sita", "Raj");