1. Fork this repository.
2. Remove the @Disabled Tags.
3. Solve the Problem.

This repository is a Java Stream API practice project built with Java 17, Maven, and JUnit 5. It helps developers learn Java streams through step-by-step notes, intermediate and terminal operation examples, and hands-on coding exercises across easy, medium, and hard difficulty levels.

If you are searching for Java Stream API exercises, Java stream interview-style practice, functional programming examples in Java, or Stream API problems with solutions, this project is designed to be a practical learning resource.

• Learn the Java Stream API from core concepts to advanced problem solving.
• Practice filter, map, flatMap, distinct, sorted, reduce, collect, and more.
• Solve JUnit-based exercises where your answer is compared against a reference solution.
• Explore related topics like functional interfaces and stream gatherers.
• Use a repository layout that is easy to study, fork, and extend.

1. Start with learn/concepts
2. Review learn/intermediate_operations
3. Review learn/terminal_operations
4. Solve practice/a_easy_problems
5. Move to practice/b_medium_problems
6. Finish with practice/c_hard_problems
7. Explore practice/functional_interfaces
8. Explore gatherer notes in learn/gatherers and gatherer exercises in practice/gatherers

For a topic-by-topic index, open TOPICS.md.

src/test/java/com/github/streams/
├── learn/
│   ├── concepts/
│   ├── gatherers/
│   ├── intermediate_operations/
│   └── terminal_operations/
└── practice/
    ├── a_easy_problems/
    │   ├── numbers/
    │   └── strings/
    ├── b_medium_problems/
    │   ├── employee/
    │   ├── numbers/
    │   └── strings/
    ├── c_hard_problems/
    │   └── numbers/
    ├── functional_interfaces/
    └── gatherers/

Each exercise follows the same pattern:

1. Open a test class under src/test/java/com/github/streams/practice/...
2. Remove the @Disabled annotation
3. Write your Stream API solution in the yourSolution variable
4. Run the test and compare your implementation against mine.

• Beginner-friendly stream fundamentals
• Stream vs collection differences
• Lazy evaluation
• Optional results
• When not to use the Streams API

• filter
• map
• flatMap
• distinct
• sorted
• peek
• limit
• skip
• takeWhile
• dropWhile
• mapMulti

• count
• forEach
• forEachOrdered
• toArray
• min / max
• anyMatch / allMatch / noneMatch
• findFirst / findAny
• reduce
• collect

• Easy number and string problems
• Medium number, string, and employee aggregation problems
• Hard number challenges such as prime streams and consecutive sequence problems
• Functional interface exercises with Predicate, Function, Consumer, Supplier, and more
• Gatherer practice for modern stream processing patterns

• Java beginners learning the Stream API
• Intermediate Java developers looking to solidify their stream knowledge
• Experienced Java engineers preparing for coding interviews that involve stream-based problems
• Developers preparing for coding interviews involving streams
• Engineers who want Java functional programming examples
• Students looking for JUnit-based practice problems with solutions

If this repository helps you learn Java streams, consider starring it so more developers can discover it.