Create multi-dimensinal ArrayList in java

Question

I want to create an arrayList as following.

id->1512   associated with the values -> 12,45,78
id->1578   associated with the values -> 456,78,87,96

What I have to do? Should I create a 2-d arrayList or can I do that with single dimension arraylist?

You need a MultiMap<Integer, Integer> (e.g. from Guava), or a Map<Integer, Set<Integer>> — jlordo
– jlordo, Commented Feb 24, 2013 at 10:05

PermGenError · Accepted Answer · 2013-02-24 10:05:15Z

5

You are looking for something like this:

Map<Integer, List<Integer>>

answered Feb 24, 2013 at 10:05

PermGenError

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5 Comments

jlordo Over a year ago

I'd prefer a MultiMap<Integer, Integer>

Aubin Over a year ago

I prefer not using third party libraries

jlordo Over a year ago

@Aubin: Why not? A MultiMap will result in much nicer code, as you don't have to null check every key.

PermGenError Over a year ago

@jlordo thanks, but never really used Guava library before .. :P. but sounds like a good one :)

jlordo Over a year ago

@PremGenError: Compare the code in my answer to what would be needed to add the key/value pairs to your Map<Integer, List<Integer>>

jlordo · Accepted Answer · 2013-02-24 10:25:07Z

2

Use the Guava Library, and you can do this for your associations:

Multimap<Integer, Integer> map = HashMultimap.create();
map.putAll(1512, Arrays.asList(12, 45, 78));
map.putAll(1578, Arrays.asList(456, 78, 87, 96));

Here's an example how you can get the values:

int key = 1512;
for (Integer value : map.get(key)) {
    System.out.println("Associated " + key + " -> " + value);
}

Here's a link to Guava's JavaDoc

edited Feb 24, 2013 at 10:25

answered Feb 24, 2013 at 10:19

jlordo

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3 Comments

jlordo Over a year ago

@Aubin: Sorry, I can't understand what your comment means in regard to my answer.

Aubin Over a year ago

Occam's razor says you have to adapt means to goals. Guava is over sized for this simple problem. Dependencies reduces the re-usability of a solution.

jlordo Over a year ago

@Aubin: Ok, makes sense now. In this case, we have to agree to disagree, because Guava makes programming this kind of map so much easier. You don't have to null check when inserting, you don't have to think about what kind of collection is used to save the values and so forth.

Shelef · Accepted Answer · 2013-02-24 10:11:51Z

0

You dont need ArrayList. read abut Map

answered Feb 24, 2013 at 10:11

Shelef

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