Explain Java Streams API and its key operations.

Streams API (Java 8+) enables functional-style operations on collections. Pipeline: source -> intermediate operations -> terminal operation. Intermediate (lazy): filter, map, flatMap, sorted, distinct, limit, skip. Terminal (eager): forEach, collect, reduce, count, findFirst, anyMatch. Parallel streams: .parallelStream() for concurrent processing. Collectors: toList, toSet, groupingBy, joining. Benefits: declarative code, parallelization, lazy evaluation. Example: list.stream().filter(x -> x > 0).map(x -> x * 2).collect(toList()). Streams are single-use; create new stream for reprocessing.