java hash tree map

/**
 * @author lautturi.com
 * Java example: print frequencies of all elements using TreeMap
 */

import java.util.*;

public class Lautturi {

	// This function prints frequencies of all elements
    static void printFreq(int arr[])
    {
        // Creates an empty TreeMap
        TreeMap<Integer, Integer> tmap =
                     new TreeMap<Integer, Integer>();

        // Traverse through the given array
        for (int i = 0; i < arr.length; i++)
        {
            Integer c = tmap.get(arr[i]);

            // If this is first occurrence of element   
            if (tmap.get(arr[i]) == null)
               tmap.put(arr[i], 1);

            // If elements already exists in hash map
            else
              tmap.put(arr[i], ++c);
        }

        // Print result
        for (Map.Entry m:tmap.entrySet())
          System.out.println("Frequency of " + m.getKey() + " is " + m.getValue());
    }
    
	public static void main(String[] args) {
		
		int[] arr = { 11,4,12,7,55,8,12,8,13,55,12,7 };
        printFreq(arr);
		
	}
}

output:

Frequency of 4 is 1
Frequency of 7 is 2
Frequency of 8 is 2
Frequency of 11 is 1
Frequency of 12 is 3
Frequency of 13 is 1
Frequency of 55 is 2