Illustration of thenRun method of CompletableFuture

ThenRunExample.java

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

public class ThenRunExample {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
            CompletableFuture<Void> completableFuture = CompletableFuture.supplyAsync(() -> {
                try {
                    // delaying the thread by 2 seconds
                    TimeUnit.SECONDS.sleep(2);
                } catch (InterruptedException e) {
                    throw new IllegalStateException(e);
                }
                return "Hello!";
            }).thenRun(() -> System.out.println("Completed after 2 seconds."));

            // get() blocks and gets the result of the Future
            completableFuture.get();
    }
}
// Output: Completed after 2 seconds.