hashmap keyset automatically sorted

问题

    HashMap<String, String[]> content = new HashMap<String, String[]>();

    content.put("Help", new String[]{"About"});
    content.put("View", new String[]{"Grid"});
    content.put("File", new String[]{"Import", "Export"});

    for(String key : content.keySet()){
        System.out.println(key);
    }

The above code logs:

View
Help
File

But why is this sorted?

回答1:

1. HashMap makes absolutely no guarantees about the iteration order. It can (and will) even change completely when new elements are added.

2. LinkedHashMap will iterate in the order in which the entries were put into the map

Source

回答2:

The order in which you see the entries in the HashMap depends on the hash codes of the keys and order of the entries in the bucket I believe and it is implementation dependent, but don't rely on HashMap for ordering at all. Whereas LinkedHashMap and TreeMap do guarantee a certain order.

来源：https://stackoverflow.com/questions/17910377/hashmap-keyset-automatically-sorted