How are Collections different from Stream?

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Collections and Streams in Java are both used for handling groups of objects, but they serve different purposes. Collections are primarily used for storing and managing data, while Streams are used for processing data in a functional manner.

  1. Purpose and Use:

    • Collections: Collections are used to store and organize data. They provide a way to manage groups of objects with various data structures like List, Set, Queue, and Map.
    • Streams: Streams are used to process data. They provide a functional approach to perform operations like filtering, mapping, and reducing on data sources.

  2. Mutability:

    • Collections: Collections are mutable. You can add, remove, or update elements in a collection.
    • Streams: Streams are immutable. Operations on a stream do not modify its source; instead, they produce a new stream with the results.

  3. Traversal:

  4. Collections: Collections can be traversed multiple times. You can iterate over the elements using loops or iterators.
  5. Streams: Streams can be traversed only once. Once a stream is consumed, it cannot be reused.