Simple Illustration of thenApply method for CompletableFuture

ThenApplyExample.java

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

public class ThenApplyExample {
    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 "World";
        }).thenApply(name -> "Hello " + name); // Attaching a callback to the Future

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