Converting Treemap keys and values to array

Question

I need to convert a TreeMap to an array; could anyone show me how it's done? I need both keys and values.I am mapping each word to its frequency in a text file

Here is output :

Bypass Internet Censorship.txt

{about=1, administrators=1, ago=1, and=1, around=1, asking=1, at=2, blocked=1, by=1, com=1, device=1, either=1, filtering=1, freerk=1, get=1, helps=1, hope=1, i=1, long=1, not=1, or=2, remember=1, school=1, sites=1, so=1, some=1, someone=1, that=1, the=1, this=1, to=1, view=1, was=1, ways=1, web=1, were=1, work=1, www=1, zensur=1}

what format do you need in arrays ? do you need a 2D array, or single dimension? surely you can iterate over the map and put the values into an array? also, why do you need an array ? — aishwarya
– aishwarya, Commented Dec 19, 2011 at 10:28
i need 2D array, i need to store them in an array to perform LSI — sum2000
– sum2000, Commented Dec 19, 2011 at 12:43
in that case, you may actually be better off with a map. Anyways, if you do need an array, use Sean's solution with Pangea's loop. — aishwarya
– aishwarya, Commented Dec 20, 2011 at 4:06

Aravind Yarram · Accepted Answer · 2011-12-19 09:55:14Z

2

    StringBuilder temp=new StringBuilder();

    for(Map.Entry<String,Integer> entry : treeMap.entrySet()) 
    {
      String key = entry.getKey();
      Integer value = entry.getValue();

      temp.append(key).append(" = ").append(value).append(", ");
    }

    //TODO remove the last comma

String result=temp.toString();

answered Dec 19, 2011 at 9:55

Aravind Yarram

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Comments

Sean Patrick Floyd · Accepted Answer · 2020-12-12 01:48:11Z

0

Don't use a TreeMap, use Guava's TreeMultiSet.

String[] str = new String[treeMultiSet.size()];
int ct = 0;
for(MultiSet.Entry<String> entry : treeMultiSet.entrySet()){
   str[ct++] = entry.getElement() + "=" + entry.getCount();
}

Update almost 10 years later:

I still think a MultiSet is better suited for the job, because the write path is much less painful, but here's a Java 8+ version of doing it with a Map (including TreeMap):

static String mapToArray(Map<String, Integer> map) {
    return map.entrySet()
              .stream()
              .map(e -> e.getKey() + "=" + e.getValue())
              .collect(Collectors.joining(", ", "{", "}"));
}

edited Dec 12, 2020 at 1:48

answered Dec 19, 2011 at 9:44

Sean Patrick Floyd

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2 Comments

sum2000 Over a year ago

actually , i am new to java ,the code which i made is very long as it involves folders, files etc. , i would prefer now not to change code , can you tell me how to do it with TreeMap.

Twonky Over a year ago

Why should we not use TreeMap? By the way, the link is dead.

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