As part of concurrency updates to JDK 9 (JEP 266), Reactive Streams was added to the Java standard library. Reactive Streams was initiated in 2013 by some of the well-known organizations that wanted to standardize the approach by which asynchronous data can be exchanged between software components. Soon, the concept became adopted by the industry and there evolved a number of implementations that all had similar core concepts but lacked standard nomenclature and terminologies, especially as regards interfaces and package naming. To avoid multiple nomenclatures and to enable interoperability between implementations, JDK 9 included basic interfaces as part of the Flow Concurrency library. This made applications want to implement Reactive Streams to depend on this library but not include specific implementations into the code base. Thus it is very easy to swap between implementations without any trouble.

These interfaces are coded as static interfaces within the java.util.concurrent.Flow class.