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This article mainly explains "example Analysis of phased Task execution in java". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn the example analysis of phased task execution in java.

CompletableFuture introduction

The CompletableFuture class implements the interface between CompletionStage and Future. CompletionStage translates to the completion phase, representing each stage of the task, and then it declares some way to deal with the task next, and CompletableFuture is its implementer.

CompletableFuture can be regarded as a unit on the pipeline, the completion of one unit can trigger the execution of the next unit, and then trigger the next, until all the units are completed, and finally produce a final result.

CompletableFuture also implements the Future interface, which represents a task executed asynchronously and can obtain the result after asynchronous completion. So the CompletableFuture can also be used as a Future,n so that the Future can be done explicitly.

So CompletableFuture represents a phase, and it can also be regarded as a task, which is equivalent to dividing the pipeline into tasks, so it is a synthesis of stages and tasks.

Introduction of main methods

CompletableFuture provides a lot of methods, and most CompletableFuture methods return a CompletableFuture before continuing to call the new method, so the phase object that invokes the method is later called the previous phase, and this method represents this phase.

Here, the methods are classified first, and the classification summary diagram is shown in the following figure:

The first is the method that ends with Async, which indicates that the phase to be executed will be executed asynchronously. Such methods can pass an executor (thread pool) into it, specifying the thread pool to execute asynchronously, and if not specified, it will be implemented by default through ForkJoinPool.

Basically, other subsequent methods can be used with Async (except anyof and allof). If the method has Async, it is executed asynchronously, otherwise it is executed synchronously.

Then let's look at the method that starts with thenApply, where thenApply can be divided into two parts:

Then indicates that the action at this stage occurs after the normal completion of the current phase.

Apply indicates that this phase takes the result returned by the previous phase (the phase object that called the method) as a parameter.

If thenApply is followed by Async, it means that the next phase will be executed asynchronously, if not, the same thread will be used to continue execution, and the latter method is similar.

Then there is a method that starts with thenAccept, which is actually similar to thenApply, except that it accepts a parameter of Consumer, that is, a deposit consumer, and does not return a value. If the next phase receives the results of the current phase, but does not need to return a value when calculating (its return type is void).

ApplyToEither can handle two phases, the current phase and the other phase passed as a parameter, and as long as one of them is completed, the other parameter fn will be executed. That is, its function is to move on to the next stage as long as any stage is completed.

The difference between acceptEither and applyToEither is the same as thenAccept and thenApply.

The runAfterBoth method is like the above method, on the contrary, you must complete the two-stage task before you can move on to the next stage.

The parameter accepted by the thenAcceptBoth method is that CompletableFuture and BiConsumer,BiConsumer can accept both of their results and then calculate them.

Similarly, the thenCombine method can also obtain the results of the first two stages, which are independent of each other, and then integrate the two results.

On the surface, thenCompose also appears to be the result of one phase on another, but it is not necessarily different. It is a new phase, which has multiple subsequent phases, and the initial result can be used as any stage of the new phase. It is as if the product of a working unit can be used as any unit of another assembly line.

The anyOf method accepts a CompletableFuture collection, as long as whenComplete (BiConsumer) is used in any completion of the collection.

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