javaInt4Bytes

Stream flatMap() in Java with examples Stream flatMap(Function mapper) returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Stream flatMap(Function mapper) is an  intermediate operation . These operations are always lazy. Intermediate operations are invoked on a Stream instance and after they finish their processing, they give a Stream instance as output. Note :  Each mapped stream is closed after its contents have been placed into this stream. If a mapped stream is null, an empty stream is used, instead. flatMap() V/s map()  : 1) map() takes a Stream and transform it to another Stream. It applies a function on each element of Stream and store return value into new Stream. It does not flatten the stream. But flatMap() is the combination of a map and a flat operation i.e, it applies a function to elements as well as flatten them. 2) map() is used for