Let us assume I have the following list .
List<String> list=new ArrayList<String>();
list.add("sultan");
list.add("Masum");
list.add("sultan");
list.add("Sorry");
list.add("sultan");
list.add("Masum");
list.add("sultan");
list.add("Tarek");
list.add("sultan");
I want to know the count of occurrence of each string in Arraylist . How can I do that ? And I also want to know the string that is occurred in this Arraylist at highest times. For this particular example, the answer is "Sultan" .
It may be helpful
int occ = Collections.frequency(list, "Masum");
occ with maximum having remembered in memory. Of course if occ > maximum then you should write somewhere the actual list's element value.If you want all the strings in the first list something you could do is:
import java.util.*;
import java.util.Map.Entry;
//...
Set<String> uniques = new HashSet(list);
Map<String, Integer> counts = new HashMap<String, Integer>();
for (String elem : uniques) {
counts.put(elem, Collections.frequency(list, elem));
}
So in the end you will have the count for each string in the map. Putting one to one...this would do the following:
As for the highest frequency, you could use the Collections.max method on the entry set like this:
Collections.max(counts.entrySet(), new Comparator<Entry<String, Integer>>() {
@Override
public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
return (o1.getValue() - o2.getValue());
}
})
Check this
Collections.frequency and THIS EXAMPLE
from this example:
System.out.println("\nExample 1 - Count 'a' with frequency");
System.out.println("a : " + Collections.frequency(list, "a"));
System.out.println("\nExample 2 - Count all with frequency");
Set<String> uniqueSet = new HashSet<String>(list);
for (String temp : uniqueSet) {
System.out.println(temp + ": " + Collections.frequency(list, temp));
}
System.out.println("\nExample 3 - Count all with Map");
Map<String, Integer> map = new HashMap<String, Integer>();
for (String temp : list) {
Integer count = map.get(temp);
map.put(temp, (count == null) ? 1 : count + 1);
}
printMap(map);
System.out.println("\nSorted Map");
Map<String, Integer> treeMap = new TreeMap<String, Integer>(map);
printMap(treeMap);
