How to get ordered HashMap from YAML?

Question

I'm trying to retrieve a Map from my config.yml file, but cannot find a way to keep the key order previously set.

classes:
 beginner: 1000
 proplayer: 2000
 admin: 5000

I know that classes's keyset gets me a Map, but the order is not as the display shows.

I need it to be in order because it's the order of classes that the player will upgrade to. So if he's beginner, he'll need to upgrade to proplayer, and so on.

I need some way to sort it out, so I can get that beginner is at index 0, in order to guess which is the next class the player will move to, in this case, proplayer (index 1), but I also need to retrieve the int value of the class, in order to charge the player the amount from the class he's moving to.

Please post some java code too so we can understand **why** you need the order. `Map`s aren't ordered. — Sanjay Manohar, Aug 24 '15 at 19:01
I'll need it to be in order because the player will upgrade from class to class in the order that they're on the yml, so I'll need to upgrade from beginner to proplayer, and not a random way around that — LeoColman, Aug 24 '15 at 19:05
Have you tried using a list? i.e. beginning lines with a minus sign `-beginner` — Sanjay Manohar, Aug 24 '15 at 19:07
e.g https://github.com/Animosity/CraftIRC/wiki/Complete-idiot's-introduction-to-yaml — Sanjay Manohar, Aug 24 '15 at 19:08

score 4 · Accepted Answer · answered Jan 24 '20 at 13:15

Ordered mappings in YAML can be specified like this:

classes: !!omap
  - beginner: 1000
  - proplayer: 2000
  - admin: 5000

See Example 2.26. Ordered Mappings in YAML Specification (1.0, 1.1 or 1.2)

Please note that it doesn't have to be supported by your YAML parser, but chances are it is (SnakeYAML does support it).
The actual type that will be used for the result is also specific to your YAML parser, but should map to most natural ordered map type in the language.

spongebob · Answer 2 · 2015-08-25T19:10:48.103

Map's implementation does not care about entries order.

Therefore, while using that classes hierarchy to easily retrieve each value, I would create a parallel list to keep track of their order.

classes:
  order:
  - beginner
  - proplayer
  - admin
  cost:
    beginner: 1000
    proplayer: 2000
    admin: 5000

List<String> orderedList = data.getStringList("classes.order");
String item = orderedList.get(0);
int cost = data.getInt("classes.cost." + item);

score 0 · Answer 3 · edited May 23 '17 at 10:27

0

In short use a list?

classes:
  - beginner: 1000
  - proplayer: 2000
  - admin: 5000

Reading it: I think that has been answered here:

how to read lists in yaml?

edited May 23 '17 at 10:27

Community

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answered Aug 24 '15 at 19:13

Sanjay Manohar

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List items are not keys. You can't assign values. – spongebob Aug 25 '15 at 12:49
This is actually a list of maps. That is permitted isn't it? – Sanjay Manohar Aug 25 '15 at 14:31

How to get ordered HashMap from YAML?

3 Answers3