ch04_streams

4. Stream API

• provides sequential or parallel aggregation functions over source data (array, collection, I/O channel, ...)
• streams have close()
  • in most cases this method doesn't have to be called explicit because streams implement AutoClosable interface
  • in fact, close the stream is only needed of it's a I/O channel as source
• as well as common Stream for any object are provided three specific streams for primitive types:
  • IntStream
  • LongStream
  • DoubleStream

Stream creation

• Stream#empty(), Stream#of(), Stream#concat()
• Stream#generate(), Stream#iterate()
  • provides infinite streams
  • should be terminated by throwing exception or clever usage e.g. anyMatch() operation

Builder

• Stream.Builder<T> add(T t)
• void accept(T t)
• Stream<T> build()

Stream pipeline

• set of operations that Stream will do
• can contain 0..n intermediate operations and exactly one terminal operation
• source data can be array, collection, I/O channel, ...
• Stream will do only if terminal operation was called
• input argument of operations is always implementation of functional interface

Terminal operations

• reduce(), min(), max(), count(), forEach(), forEachOrdered(), collect(), toArray(), iterator(), spliterator()

Short-circuiting terminal operations

• findFirst(), findAny(), allMatch(), anyMatch(), noneMatch()

Intermediate operations

• peek(), map(), flatMap(), filter(), parallel(), sequential(), onClose(), unordered()

Stateful intermediate operations

• distinct(), sorted()

Short-circuiting intermediate operations

• limit(), skip()

...TBD...