Order of set screwed up

Question

I want to print values of a set, so I have following method:

private void printPubs(){
   Set<String> pubWords = new HashSet<>();
   pubWords.add("Watch");
   pubWords.add("on");
   pubWords.add("youtube");
   pubWords.add(":");
   pubWords.add("Mickey");
   pubWords.add("en");
   pubWords.add("de");
   pubWords.add("stomende");
   pubWords.add("drol");

   for (String word : pubWords){
      System.out.print(word + " ");
   }
}

Now I expected to see: "Watch on youtube: Mickey en de stomende drol" but I got "on stomende drol Watch Mickey youtube:"

How does this come?