Package java9.util.concurrent

Covers a backport of the upgraded (JEP 266) Java 9 CompletableFuture API for Java 6 to 8 and Android developers.

See: Description

Interface Summary

Interface	Description
CompletableFuture.AsynchronousCompletionTask	A marker interface identifying asynchronous tasks produced by async methods.
CompletionStage<T>	A stage of a possibly asynchronous computation, that performs an action or computes a value when another CompletionStage completes.

Class Summary

Class	Description
CompletableFuture<T>	A Future that may be explicitly completed (setting its value and status), and may be used as a CompletionStage, supporting dependent functions and actions that trigger upon its completion.

Exception Summary

Exception	Description
CompletionException	Exception thrown when an error or other exception is encountered in the course of completing a result or task.

Package java9.util.concurrent Description

Covers a backport of the upgraded (JEP 266) Java 9 CompletableFuture API for Java 6 to 8 and Android developers. See JEP 266: More Concurrency Updates.

Memory Consistency Properties

Chapter 17 of The Java™ Language Specification defines the happens-before relation on memory operations such as reads and writes of shared variables. The results of a write by one thread are guaranteed to be visible to a read by another thread only if the write operation happens-before the read operation. The synchronized and volatile constructs, as well as the Thread.start() and Thread.join() methods, can form happens-before relationships. In particular:

• Each action in a thread happens-before every action in that thread that comes later in the program's order.
• An unlock (synchronized block or method exit) of a monitor happens-before every subsequent lock (synchronized block or method entry) of that same monitor. And because the happens-before relation is transitive, all actions of a thread prior to unlocking happen-before all actions subsequent to any thread locking that monitor.
• A write to a volatile field happens-before every subsequent read of that same field. Writes and reads of volatile fields have similar memory consistency effects as entering and exiting monitors, but do not entail mutual exclusion locking.
• A call to start on a thread happens-before any action in the started thread.
• All actions in a thread happen-before any other thread successfully returns from a join on that thread.

Since:

9