How to Count Repetition of Words in Array List?

Question

I\'ve these code for searching occurrence in Array-List but my problem is how I can get result out side of this for loop in integer type cause I need in out side , may be th

Answer 1

Set unique = new HashSet(list);

and

Collections.frequency(list, key);

are too much overhead.

Here is how i would do it

List list = new ArrayList();
list.add("aaa");
list.add("bbb");
list.add("aaa");

Map countMap = new HashMap<>();


for (String word : list) {
    Integer count = countMap.get(word);
    if(count == null) {
        count = 0;
    }
    countMap.put(word, (count.intValue()+1));
}

System.out.println(countMap.toString());

Output

{aaa=2, bbb=1}

EDIT output one by one: iterate over the set of entries of the map

for(Entry entry : countMap.entrySet()) {
    System.out.println("frequency of '" + entry.getKey() + "' is "
          + entry.getValue());
}

Output

frequency of 'aaa' is 2
frequency of 'bbb' is 1

EDIT 2 No need for looping

String word = null;
Integer frequency = null;

word = "aaa";
frequency = countMap.get(word);
System.out.println("frequency of '" + word + "' is " +
    (frequency == null ? 0 : frequency.intValue()));

word = "bbb";
frequency = countMap.get(word);
System.out.println("frequency of '" + word + "' is " + 
    (frequency == null ? 0 : frequency.intValue()));

word = "foo";
frequency = countMap.get(word);
System.out.println("frequency of '" + word + "' is " + 
    (frequency == null ? 0 : frequency.intValue()));

Output

frequency of 'aaa' is 2
frequency of 'bbb' is 1
frequency of 'foo' is 0

Note that you will always have a collection and you need extract the count from it for a particular word one way or another.