Illustration of thenCombine method of CompletableFuture

ThenCombineExample.java

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class ThenCombineExample {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> {
            try { // delaying the thread by 2 seconds
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                throw new IllegalStateException(e);
            }
            return "Hello";
        }).thenCombine(CompletableFuture.supplyAsync(() -> " World!"), //combining the two CompletableFuture results
                (msg1, msg2) -> msg1 + msg2); // thenCombine() accepts a future and fn with two args to execute the task

        // get() blocks and gets the result of the Future
        System.out.println(completableFuture.get());
    }
}