How to count duplicated items in Java List........

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
 
public class CountDuplicatedList {
 
  public static void main(String[] args) {
 
 List<String> list = new ArrayList<String>();
 list.add("a");
 list.add("b");
 list.add("c");
 list.add("d");
 list.add("b");
 list.add("c");
 list.add("a");
 list.add("a");
 list.add("a");
 
 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);
 
  }
 
  public static void printMap(Map<String, Integer> map){
 
 for (Map.Entry<String, Integer> entry : map.entrySet()) {
  System.out.println("Key : " + entry.getKey() + " Value : "
   + entry.getValue());
 }
 
  }
 
}

Output

Example 1 - Count 'a' with frequency
a : 4
 
Example 2 - Count all with frequency
d: 1
b: 2
c: 2
a: 4
 
Example 3 - Count all with Map
Key : d Value : 1
Key : b Value : 2
Key : c Value : 2
Key : a Value : 4
 
Sorted Map
Key : a Value : 4
Key : b Value : 2
Key : c Value : 2
Key : d Value : 1