ExecutorService deadlocked nested tasks example

ExecutorDeadLockExample.java

package com.example;

import lombok.val;

import java.util.concurrent.*;

public class ExecutorDeadLockExample {

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        val executorService = Executors.newFixedThreadPool(1);

        /*
         * !!! THIS IS GOING TO BLOCK FOREVER !!!
         * Because the executor service is fixed to a single thread and therefore there are no available threads to run
         * nested tasks.
         */
        System.out.printf("Example 1 returned: %d\n\n",
                CompletableFuture.supplyAsync(() -> {
                    System.out.printf("1: %s\n", Thread.currentThread().getName());
                    return CompletableFuture.supplyAsync(() -> {
                        System.out.printf("2: %s\n", Thread.currentThread().getName());
                        return CompletableFuture.supplyAsync(() -> {
                            System.out.printf("3: %s\n", Thread.currentThread().getName());
                            return CompletableFuture.supplyAsync(() -> {
                                System.out.printf("4: %s\n", Thread.currentThread().getName());
                                return 1;
                            }, executorService).join();
                        }, executorService).join();
                    }, executorService).join();
                }, executorService).join()
        );
    }
}