Jedis does not delete keys

I have just installed redis' last version on Ubuntu 18.04.3. I have tried out writing values directly with redis-cli.

127.0.0.1:6379> set myket somevalue

I am now trying to delete all values from Jedis:

    Jedis jedis = new Jedis("localhost", 6379);
    Set<String> names=jedis.keys("NAME:*");
    System.out.println("There are " + names.size() +  " keys to delete");
    Iterator<String> it = names.iterator();
    while (it.hasNext()) {
        String s = it.next();
        jedis.del(s);
        System.out.println(s + " has been deleted");
    }

However, it always says that there are 0 keys right now. When I query it from redis-clidirectly, it is still there. How can I delete the keys from Jedis?