stream api

Stream Operations

A stream represents a sequence of elements and supports different kind of operations to perform computation upon those elements. The stream() method returns a sequential stream where as parallelStream() method returns a parallel stream. Look here for good explonation.

List<String> myList =
    Arrays.asList("a1", "a2", "b1", "c2", "c1");

myList
    .stream()
    .filter(s -> s.startsWith("c"))
    .map(String::toUpperCase)
    .sorted()
    .forEach(System.out::println);

// C1
// C2

Intermediate Operations

• filter
• map
• mapToInt
• mapToLong
• mapToDouble
• flatMap (create one stream of all substreams)
• flatMaptoInt
• flatMaptoLong
• flatMaptoDouble
• distinct (keeps the first appearance of any duplication)
• sorted (sorts according to natural order)
• sorted(comparator) sorted according to comparator
• peek(action) allows peeking into the stream while stream is not final, useful for debugging and logging.
• limit(maxSize) truncates the stream to the maxSize.
• discard(n) discards the first n elements in the stream

Terminal Operations

• forEach(action) performs an action for each element of this stream.
• forEachOrdered(action) Performs an action for each element of this stream, in the encounter order of the stream if the stream has a defined encounter order.
• toArray returns an object array
• toArray(IntFunction<A[]> generator)
• reduce(a,b), example: numbers.stream().reduce(0, Integer::sum); //sums up all values in the stream.