The JDK 9 java.util.concurrent.Flow class implements features from the Reactive Streams spec that provide non-blocking concurrency by supporting "push" style operations for items from an active source as they become available. This is the tip of the iceberg on the quest for reactive programming and reactive style applications.

Starting with Doug Lea's own perspective on why it's important to have these contracts in the JDK and how they relate to other async/parallel APIs in the JDK such as CompletableFuture and java.util.Stream, we'll then look at the ecosystem of reactive libraries that has emerged around Reactive Streams from async composition libraries like RxJava to non-blocking versions of existing libraries like MonoDB, CouchBase, and others, and understand the reactive programming model they enable, why it matters, and how it changes they way you think about and write non-blocking application logic.