java-streams-api

Use the Streams API to chain filter() and map() operations on collections. Filter removes elements matching a condition, map transforms each element, and terminal operations like collect() gather results into a new collection.

Java Streams enable declarative data processing with functional operations. Create a stream from your collection, apply intermediate operations like filter, map, and sorted, then use terminal operations such as collect() or forEach() to produce results.

Use flatMap() in the Streams API to flatten nested structures. FlatMap applies a function returning a stream to each element, then merges all resulting streams into a single stream before terminal collection.

Yes, Streams support chainable intermediate operations like filter, map, flatMap, distinct, and sorted. Operations execute lazily—only when you apply a terminal operation like collect(), forEach(), or reduce() does processing actually occur.

Use reduce() to combine stream elements into a single value through aggregation; use collect() to gather results into a collection or perform mutable reduction. Reduce is suited for computing sums, products, or other scalar results from streams.

No, but understanding lambda expressions and method references helps. Streams API handles the functional complexity; start with simple filter and map chains, then progress to intermediate operations like flatMap and terminal operations as needed.