Java 8 : CompletableFuture - Multithreading framework to allow asynchronous programming

What is CompletableFuture? How to use CompletableFuture? How to execute independent multiple tasks in parallel?

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package demo.multi.threading;

import

import java.util.Arrays;
import
import java.util.stream.Collectors;

public class CompletableFutureTest {
static DummyService service = new DummyService();

public static void main(String[] args) throws Exception{

CompletableFuture<Void> future1 = CompletableFuture
.supplyAsync( () -> service.method1("1") )
.thenAccept( result -> {
System.out.println("Result1: "+result);
});
System.out.println("future1 executed!");

CompletableFuture<Void> future2 = CompletableFuture
.supplyAsync( () -> service.method2("2") )
.thenAccept( result -> {
System.out.println("Result2: "+result);
});
System.out.println("future2 executed!");

CompletableFuture<Void> future3 = CompletableFuture
.supplyAsync( () -> service.method3("3"))
.thenAccept( result -> {
System.out.println("Result3: "+result);
});
System.out.println("future3 executed!");

Arrays.asList(future1, future2, future3).stream()
.map( CompletableFuture::join )



}

}