Get Player In Radius

    Bukkit.getScheduler().scheduleSyncRepeatingTask(Main.config, new Runnable() {

        @Override
        public void run() {
            for (Entity perto : p.getNearbyEntities(7.0D, 7.0D, 7.0D)) {
                if (perto instanceof Player) {
                    final Player hit = (Player) perto;
                    hit.damage(3.0D);
                }
            }
        }
    }, 0L, 5L * 20L);