makes it possible to connect data 沈むs and sources.
The 前任者-member is the element in the 関係 that is
nearer to the source of the data. The 後継者-member is the element
that is その上の away from the source of the data. (公式文書，認める that this
分類 does not depend on whether the class 器具／実施するs
XInputStream or XOutputStream; it only
depends on the direction of data flow.)
This interface 許すs generic services to navigate between
独断的な elements of a 関係.
