Multithreading tool class completabilefuture

Detailed introduction

Java8 CompletableFuture Use it all
CompletableFuture Detailed explanation （ One ）： Basic concepts and usage

Categories and examples

CompletableFuture The use of,
JDK1.8 New characteristics CompletableFuture summary
Future and CompletableFuture Use
CompletableFuture Learning record
The multithreading CompletableFuture Use

Easy to understand

With Future and Executor To perform our asynchronous tasks Why do you need this ？
use Future Get asynchronous execution results There are two ways ： call Get() perhaps polling isDOne() Is it True

 Neither of these methods is very good , Because the main thread will also be forced to wait 

To reduce this wait JAVA8 Introduced this CP Yes Future Improvements have been made. You can pass in the callback object

Create a class

completeFuture  Can be used to create default return values 
runAsync  Asynchronous execution , No return value 
supplyAsync  Asynchronous execution , There is a return value 
anyOf  Any execution is complete , You can take the next step 
allOf  Complete all tasks , Before we can carry out the next task 

//  Asynchronous task , No return value , Internal forkjoin Thread pool 
CompletableFuture c1 = CompletableFuture
.runAsync(()->{
    System.out.println(" Turn on the switch , Start making , Don't worry about it ")});

//  Asynchronous task , No return value , Use a custom thread pool 
CompletableFuture c11 = CompletableFuture
.runAsync(()->{
    System.out.println(" Turn on the switch , Start making , Don't worry about it ")},newSingleThreadExecutor());

//  Asynchronous task , There is a return value , Use the internal default thread pool 
CompletableFuture<String> c2 = CompletableFuture
.supplyAsync(()->{
    System.out.println(" Wash the rice ");return " Clean rice ";});

//  As long as there is one finish , Then finish , There is an exception thrown , It carries an exception 
CompletableFuture.anyOf(c1,c2);

//  Have to wait for all future Only when it's all finished 
CompletableFuture.allOf(c1,c2);

State value class

join  Consolidated results , wait for 
get  Merge and wait for results , You can increase the timeout ;get and join difference ,join It just throws unchecked abnormal ,get Will return a specific exception 
getNow  If the result calculation is completed or abnormal , Results or exceptions are returned ; otherwise , return valueIfAbsent Value 
isCancelled
isCompletedExceptionally
isDone

//  Don't throw exceptions , A blocked wait 
future.join()
//  Throw an exception if there is an exception , A blocked wait , Wait indefinitely 
future.get()
//  Throw an exception if there is an exception , The longest wait 1 Hours , An hour later , If there's no data yet , Is abnormal .
future.get(1,TimeUnit.Hours)

The control class For active control CompletableFuture The act of completing

complete
completeExceptionally
cancel

3 Ways of planting ：
//  complete 
future.complete(" Steamed Rice ");
//  abnormal 
future.completeExceptionally();
//  Cancel , Parameters have no practical meaning , No eggs .
future.cancel(false);

In the class

CompletableFuture The most important feature , Without this ,CompletableFuture It doesn't make sense , This property is Inject callback behavior .
There are many ways to connect , It can be summarized into three categories ：

CompletableFuture + (Runnable,Consumer,Function)
CompletableFuture + CompletableFuture
CompletableFuture +  Processing results 

CompletableFuture future = CompletableFuture.supplyAsync(()->{
    
    System.out.println(" Put in and wash the materials for making rice ");
    return " Clean rice without COVID-19. ";
}).thenAcceptAsync(result->{
    
    System.out.println(" Electrify , Set mode , Start cooking rice ");
}).thenRunAsync(()->{
    
    System.out.println(" The rice is ready , You can eat ");
})

Summary memory

 With  Async  ending   Methods , All are   Asynchronous methods , Corresponding   No,  Async  It is   Synchronization method , Generally, an asynchronous method corresponds to a synchronous method .
 With  Async  The suffix ends   Methods , There are   Two heavy loads   Methods , One is   Use default  forkjoin  Thread pool , One is to use   Custom thread pool 
 With  run  Opening method , The entry parameter must be   No arguments   Of , also   no return value  , Similar to the execution of Runnable Method .
 With  supply  Opening method , The entrance is also   No parameters   Of , however   There is a return value 
 With  Accept  Beginning or end   Methods , The entry parameter is   With parameters , however   no return value 
 With  Apply  Beginning or end   Methods , The entry has parameters , There is a return value 
 with  either  suffix   Methods , Express   Whoever finishes first will consume