java-stream-api

Explore and master Java Streams with over 50 practical, real-world examples.

This repository contains concise, commented, and well-structured Java examples that demonstrate how to use the Java Stream API for efficient and modern data processing. Each example focuses on a common data transformation or query operation — from filtering and mapping, to advanced grouping and aggregation.

Features

50+ Realistic Examples
Find, filter, map, reduce, group, sort, combine, and transform data using Stream API with intuitive, idiomatic Java code.
Educational & Practical
Each example is presented as a separate, easily understandable static method with clear naming and documentation, making it great for learning, interviews, or reference.
Covers Core Stream API Use Cases
Including:
- Filtering and searching
- Mapping and transforming
- Distinctness and deduplication
- Sorting and ordering
- Reducing, aggregating, and summarizing
- Working with objects
- Advanced grouping and partitioning
- Optional usage and null safety
- Collectors and downstream collectors

Example Topics

Counting, summing, averaging, finding min/max
Combining and joining strings or lists
Extracting, flattening, and mapping nested structures
Grouping and partitioning data
Generating and processing random data
Working with custom objects and collections

Getting Started

Clone the repo:
git clone https://github.com/javadev/java-stream-api.git
Open in your favorite IDE
Run the main class (App.java) to execute all examples, or call any method independently.

Who Is This For?

Java learners wishing to deepen practical knowledge
Java developers needing quick reference or copy-paste solutions
Instructors/interviewers looking for demonstration snippets
Anyone exploring the power of functional programming in Java!

Contribution

Contributions and new stream examples are welcome! Please open an issue or PR.

Let me know if you want a shorter/longer version, or want help with a README including formatting!

javadev/java-stream-api