Java Tutorial: Lambdas & Streams
Lambda expressions, method references, and the Stream API — filter, map, reduce, collect, sorted, and parallel streams.
Data pipelines without the boilerplate
Streams let you process collections with a declarative pipeline — tell Java WHAT to do, not HOW to loop.
Before Streams: 20 lines of for-loops and conditionals. After Streams: 3 lines of filter/map/collect. Not just shorter — easier to read and reason about.
What you'll learn in this Java lambdas & streams tutorial
This interactive Java tutorial has 7 hands-on exercises. Estimated time: 22 minutes.
- Lambda expressions — Lambdas are inline function implementations. They implement functional interfaces:
- Method references — Method references are shorter lambdas when you just call an existing method:
- Stream basics — filter and map — A Stream pipeline: source → intermediate operations → terminal operation.
- reduce, sorted, distinct — More stream operations:
- Collectors — grouping and joining — `Collectors` provides powerful terminal operations:
- Optional — null safety — `Optional<T>` wraps a value that might not exist — it forces you to handle the missing case.
- Build a report generator — Final challenge — no starter code.
Java Lambdas & Streams concepts covered
- Data pipelines without the boilerplate