How can I put a hashmap inside an array? conf[0] = new HashMap();

Question

How can I put a hashmap inside an array?

HashMap<String, Object>[] config= null;
        config[0] = new HashMap<String, Object>(); 
        config[0].put("Name", "Jon");
        config[0].put("valueA", 0);
        config[1] = new HashMap<String, Object>(); 
        config[1].put("valueA", 2323);

This is Array of HashMaps, And you have to initialized array with some size — Pragnani, May 28 '13 at 13:29

Woot4Moo · Accepted Answer · 2013-05-28T13:38:11.970

4

List<Map<String, String>[]> listOfMaps = new ArrayList<Map<String, String>[]>();

should be sufficient. You don't instantiate it with the () since it is an array, you need to provide it a size or a series of HashMaps as part of the array constructor.

edited May 28 '13 at 13:38

answered May 28 '13 at 13:28

Woot4Moo

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Thanks you! But How Can I do this without provide a size? Is it possible? if I use your code I get the following error: "Cannot create a generic array of HashMap" – ephramd May 28 '13 at 13:34
I see :) I'll remove my comment – Vincent van der Weele May 28 '13 at 13:39
@Heuster it was my mistake, gotta stop trusting my memory :) – Woot4Moo May 28 '13 at 13:40
Why make it a List of Map arrays? Why not just a List of Maps? – Tom McIntyre May 28 '13 at 13:58
@TomMcIntyre because OP wants it to be an array – Woot4Moo May 28 '13 at 14:01

score 1 · Answer 2 · edited May 23 '17 at 12:18

1

You can find some explanation here What's the reason I can't create generic array types in Java?

I propose to use next construction:

ArrayList<HashMap<String, Object>> config= new ArrayList<HashMap<String,Object>>();
HashMap<String, Object> map;
map = new HashMap<String, Object>();        
map.put("Name", "Jon");
map.put("valueA", 0);       
config.add(map); 
map = new HashMap<String, Object>();        
map.put("valueA", 2323);                        
config.add(map);

edited May 23 '17 at 12:18

Community

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answered May 28 '13 at 13:40

Ilya Gruzinov

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Thanks! It's works! And for read: `config.get(0).get("Name"); //Jon` edit/add: `config.get(0).put("Name", "Snow"));` – ephramd May 29 '13 at 07:00

score 0 · Answer 3 · edited May 23 '17 at 12:28

0

Whilst you can declare an array of generics, you cannot instantiate them using the normal syntax.

Map<String,Object>[] config = new HashMap<String,Object>[10]; would give the compile error: Cannot create a generic array of HashMap

You can however use Array.newInstance see answers to this SO question

edited May 23 '17 at 12:28

Community

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answered May 28 '13 at 13:37

FunkTheMonk

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score 0 · Answer 4 · answered May 28 '13 at 13:38

0

use ArrayList instead of a simple array.

            ArrayList<HashMap<String, Object>> arrayOfMap=new ArrayList<HashMap<String,Object>>();

answered May 28 '13 at 13:38

anddevmanu

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why we put '0' at end of some HashMap ? ex : 'new hashmap<>(0);' why we not use 'new hashmap<>();' – Priyan RockZ Dec 08 '13 at 05:15

score 0 · Answer 5 · answered May 28 '13 at 13:39

0

Map<String,Object>[] config = new HashMap[10];

just leave the generic parameters away.

answered May 28 '13 at 13:39

kutschkem

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How can I put a hashmap inside an array? conf[0] = new HashMap();

5 Answers5