java multi mapping arraylist

Question

Is it possible to map key to Multi Dimensional Array List. Some thing like following example..

Map<K,V>

Where K is key for list of alphabet and V is a multi dimensional array list or normal array list that stores list of word. Some thing like a application that reads a dictionary file. I want to see an example. Example can be anything related to Map and Multi Dimensional Array-list. Or is there any other efficient way to implement collection? I have never used such implementations so if there is already a thread related to mine QA please post the link.

I82Much · Accepted Answer · 2011-12-25 19:08:41Z

7

You can always do Map<String, <List<String>>. e.g.

Map<String, List<String>> multimap = new HashMap<String, List<String>>();
String key = "asdf";
List<String> values = Arrays.asList("foo", "bar");
multimap.put(key, values);

You can also use the Multimap<String, String> interface in Google Guava - might be a better fit for your needs. It simplifies the coding somewhat -

Multimap<String, String> multimap = new ArrayListMultimap<String, String>();
String key = "asdf";
multimap.put(key, "foo");
multimap.put(key, "bar");

edited Dec 25, 2011 at 19:08

answered Dec 25, 2011 at 19:06

I82Much

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Comments

Aravind Yarram · Accepted Answer · 2011-12-25 19:07:12Z

5

You can use Guava's Multimap's if you want to associate multiple values with a single key. You need ArrayListMultimap for your specific case.

Example

ListMultimap<String, String> dict= new ArrayListMultimap<String, String>();
dict.put("key 1", "value 1");
dict.put("key 1", "value 2");
dict.put("key 2", "value 1");

answered Dec 25, 2011 at 19:07

Aravind Yarram

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4 Comments

Defozo Over a year ago

'ArrayListMultimap()' has private access in 'com.google.common.collect.ArrayListMultimap' What am I doing wrong?

Defozo Over a year ago

Shouldn't it be Multimap<String, String> multimap = ArrayListMultimap.create(); instead?

Istvan Devai Over a year ago

Above Guava 21 both new ArrayListMultimap<String, String>(); and ArrayListMultimap.create(); are deprecated. The new style is: ListMultimap<String, Integer> result = MultimapBuilder.hashKeys().arrayListValues().build() enjoy :)

Istvan Devai Over a year ago

To be precise ArrayListMultimap.create(); works, but in the documentation it is marked as "soon to be deprecated".

Somnath Kadam · Accepted Answer · 2013-02-14 15:46:47Z

4

Following code without Google's Guava library. It is used for double value as key and sorted order

Map<Double,List<Object>> multiMap = new TreeMap<Double,List<Object>>();

for( int i= 0;i<15;i++)
{
    List<Object> myClassList = multiMap.get((double)i);
    if(myClassList == null)
    {
        myClassList = new ArrayList<Object>();
        multiMap.put((double) i,myClassList);
    }
    myClassList.add("Value "+ i);
}

List<Object> myClassList = multiMap.get((double)0);
if(myClassList == null)
{
    myClassList = new ArrayList<Object>();
    multiMap.put( (double) 0,myClassList);
}
myClassList.add("Value Duplicate");
for (Map.Entry entry : multiMap.entrySet()) 
{
  System.out.println("Key = " + entry.getKey() + ", Value = " +entry.getValue());
}

edited Feb 14, 2013 at 15:46

answered Feb 14, 2013 at 15:16

Somnath Kadam

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