lambdas and streams

functions as values, and pipelines that process data lazily, one element at a time.

1. 01lambdassyntax, target typing, and why captured variables must be effectively final.
2. 02functional interfacesFunction, Supplier, Consumer, Predicate and the rest of the zoo.
3. 03method referencesthe four kinds of ::, and what each one desugars to.
4. 04how a stream pipeline runssource → intermediate → terminal. lazy, one element at a time.
5. 05stream operationsmap, filter, flatMap, sorted, distinct, limit, takeWhile.
6. 06collectorstoList, groupingBy, partitioningBy, toMap, teeing.
7. 07reductionreduce with identity, accumulator, combiner. and when to use collect instead.
8. 08primitive streamsIntStream and friends, and the cost of boxing.
9. 09gatherersjava 24+custom intermediate operations: windows, scans, and mapConcurrent.
10. 10parallel streamsspliterators, the common pool, and when parallel is slower.