Strange thing with CompletableFuture

gistfile1.txt

        System.out.println("CompletableFuture");
        Future<String> foo = new CompletableFuture<>();
        System.out.println(foo.cancel(true));
        System.out.println(foo.cancel(true));

        System.out.println("Guava SettableFuture");
        foo = SettableFuture.create();
        System.out.println(foo.cancel(true));
        System.out.println(foo.cancel(true));

        System.out.println("Spring SettableListenableFuture");
        foo = new SettableListenableFuture<>();
        System.out.println(foo.cancel(true));
        System.out.println(foo.cancel(true));

        System.out.println("Real Future");
        foo = Executors.newSingleThreadScheduledExecutor().submit(() -> {
            try {
                Thread.sleep(TimeUnit.DAYS.toMillis(1));
            } catch (InterruptedException e) {
                //ignore
            }
            return "foo";
        });
        System.out.println(foo.cancel(true));
        System.out.println(foo.cancel(true));