Problem counting in Map<String, Integer>

Question

Hi, I asked a question about counting the number of times a word is in ArrayList:

ACU ACU ACU ACU ACY ACY AER AER AER AGC

So for
ACU we will get 4,
ACY we will get 2,
AER we will get 3,
AGC we will get 1.

I got some help but I cannot make it work.
Darren gave me a very important answer:

Map<String, Integer>wordCount = new HashMap<String, int>();
  for(String seq : yourWordList){
     wordCount.put(seq, wordCount.get(seq++));
  }

But in the part wordCount.put(seq, wordCount.get(seq++)); I get an error that cannot convert from String to int, I tried to modify the code to work but I'm getting incorrect numbers

ACU 0 ACU 1 ACU 1 ACU 1 ACY 1 ACY 2 AER 2 AER 3 AER 3

int value=0;
Map<String, Integer>wordCount = new HashMap<String, Integer>();
for(String seq : WordList){
  Set<String> set = wordCount.keySet();
  value = set.size();
  wordCount.put(seq, value));
}

Please help me on this one. Thanks to all.

Answer 1

wordCount.get(seq++) is probably the issue--try incrementing the return value of the get method (right now you're apparently attempting to increment the String argument, triggering the error. Try changing that to wordCount.get(seq)+1

Answer 2

Alternative solution that uses Multiset from Google Collections.

Multiset<String> words = HashMultiset.create();
for (String word : wordList)
    words.add(word);

for (String word : words.elementSet())
    System.out.println(word + ": " + words.count(word));

Answer 3

What you want is:

Map<String, Integer>wordCount = new HashMap<String, Integer>();
for (String seq : yourWordList) {
  Integer count = wordCount.get(seq);
  wordCount.put(seq, count == null ? 1 : count + 1);
}

The Map is from String to Integer. Integer is immutable so you can't increment it in place. You have to retrieve the current value, increment it and put it back. You're trying to call wordCount.get(seq++), which doesn't make a lot of sense. get() has to be passed in a String (for this kind of Map) and you can't use ++ on an immutable Integer anyway.