Map of words and their occurence [ Reverse Version ]

[Goldstein]

Hey everyone,

as written in the title im having trouble creating the reverse version of this code :
for each word i associate its number of occurences.

public static Map<String,Integer> orc(ArrayList<String> l)
{


Map<String,Integer> m = new TreeMap<String,Integer>();
for (int j=0; j < l.size() ; j++)
{
int cpt=0;
for (int i=0; i < l.size() ; i++)
{
if ( l.get(i).equals(l.get(j)))
{cpt++;}
}
m.put(l.get(j), cpt);
}
return m;

}

Now i want to create a map<Integer,Set<String>> which contains each number of occurence and the list of words who exists the same number of times:

for example: 2 = { a,b,c} 1 = {d,e}

Thank you :)

[pbrockway2]

Go through your first map and add for each string/count pair add it to the new map. Adding to the new map will involve (1) creating a new entry for that count if one does not already exist and (2) adding the string to the count's associated set.

(I had a look at the extensive Guava library, but couldn't find a method that transforms maps like this. There is a MultiMap class, though, which allows duplicate values to be added.)

[Edit] I knew I'd seen it somewhere! Guava does have an inverse() method - but only for ImmutableMultiMap<K,V>.