How to give the static value to HashMap?

Question

I have HashMap like:

static HashMap<String,ArrayList<Media>> mediaListWithCategory=new HashMap<String,ArrayList<Media>>();

I have value like:

January:
   -Sunday
   -Monday
Februsry:
   -Saturday
   -Sunday
   -Thursday
March:
   -Monday
   -Tuesday
   -Wednesday

How can I statically assign these values when defining the hash map?

score 9 · Accepted Answer · answered Nov 21 '11 at 12:32

9

You can populate it in a static block:

static {
   map.put("January", Arrays.asList(new Media("Sunday"), new Media("Monday")));
}

(You should prefer interface to concrete classes. define your type as Map<String, List<Media>>)

answered Nov 21 '11 at 12:32

Bozho

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If it is String instead of the Media then should i have to define "new" keyword for the new string object ? – Shreyash Mahajan Nov 21 '11 at 12:36
ok. I have solve it by this one: mediaListWithCategory.put("January",(ArrayList) Arrays.asList("sunday","gdahdga") ); – Shreyash Mahajan Nov 21 '11 at 12:43

score 4 · Answer 2 · answered Nov 21 '11 at 12:32

4

Use a static block:

static {
  mediaListWithCategory.put(youKey, yourValue);
}

answered Nov 21 '11 at 12:32

ewan.chalmers

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If there ia multiple value in to yourValue then ? – Shreyash Mahajan Nov 21 '11 at 12:39
You can write whatever code is appropriate in the static block. I thought your question was about static initialization. Do you need help in constructing your map structure? – ewan.chalmers Nov 21 '11 at 12:51

score 1 · Answer 3 · edited May 23 '17 at 12:09

A variant of this may be more succinct:

static HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>() {{
    put("January", new ArrayList<String>() {{
        add("Sunday");
        add("Monday");
      }});
    put("Februsry" /* sic. */, new ArrayList<String>() {{
        add("Saturday");
        add("Sunday");
        add("Thursday");
      }});
    put("March", new ArrayList<String>() {{
        add("Monday");
        add("Tuesday");
        add("Wednesday");
      }});
}};

See Double Brace Initialisation for discussion.

How to give the static value to HashMap?

3 Answers3

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