Overview

This microservice demonstrates the power of Java 8 Streams using a complex JSON dataset of customers, orders, and products. It covers all major Stream operations, including:

Filtering: filter(), anyMatch(), allMatch(), noneMatch()

Mapping: map(), mapToDouble(), flatMap()

Sorting: sorted()

Reduction: reduce(), sum(), max()

Collecting: collect(), Collectors.groupingBy(), Collectors.toList(), Collectors.joining()

Parallel Streams: parallelStream() for performance testing

Matching & Validation: allMatch, anyMatch, noneMatch

Aggregation: Total revenue, spending per customer, top products

Advanced operations: Optional, Map.Entry, and LinkedHashMap usage for sorted results

This project is perfect for learning, showcasing, and experimenting with Java 8 Stream API features.

Features / Endpoints

Get all customer names

Concatenate all customer names into a single string

Retrieve orders for a customer by ID

Get the latest order per customer

Fetch top N most expensive products

Get frequently purchased products

Compute total revenue (sequential & parallel)

Find big spenders

Check customer data validation: emails, order existence

Find the most expensive product

All endpoints are fully documented with Swagger/OpenAPI, including request parameters and example responses.