Why are the Collection and Map interfaces different, even though they are in the same framework?

The Framework Collection contains two main groups of collections:

• Collection: Stores groups of objects. Elements can be duplicates (in List) or unique (in Set).
• Map: Stores pairs of "key-value". Keys are unique, values can be duplicated.

The differences are fundamental in their purpose and data structure:

• Collection: Represents a set of elements. The main operation is iterating over the elements.
• Map: Represents a mapping of keys to values. The main operation is retrieving a value by its key.

Examples of main methods:

Interface	Method	Purpose
Collection	add(E e)	Add an element
Collection	iterator()	Get an iterator
Collection	contains(Object o)	Check for the presence of an element
Map	put(K key, V value)	Associate a value with a key
Map	get(Object key)	Get a value by key
Map	keySet()	Get the set of keys

Thus, despite being part of the same framework, their goals and mechanisms of operation differ radically, which explains the existence of two separate root interfaces.