A mutable builder for a Stream. This allows the creation of a Stream by generating elements individually and adding them to the Builder (without the copying overhead that comes from using an ArrayList as a temporary buffer.)

A stream builder has a lifecycle, which starts in a building phase, during which elements can be added, and then transitions to a built phase, after which elements may not be added. The built phase begins when the build() method is called, which creates an ordered Stream whose elements are the elements that were added to the stream builder, in the order they were added.