Find the frequency of each element in an array in java

Java program for Find the frequency of each element in an array. Here problem description and other solutions.

/*
  Java program
  Count frequency of each element in array 
*/
import java.util.HashMap;
public class Occurrence
{
	// Function which is display array elements
	public static void display(int[] arr)
	{
		for (int i = 0; i < arr.length; ++i)
		{
			System.out.print("   " + arr[i]);
		}
		System.out.print("\n");
	}
	// Count occurrence of given array
	public static void frequency(int[] arr)
	{
		// Display given array
		display(arr);
		// Create a empty map
		HashMap < Integer, Integer > map = 
          new HashMap < Integer, Integer > ();
		for (int i = 0; i < arr.length; i++)
		{
			if (map.containsKey(arr[i]))
			{
				// When key exists then update value
				map.put(arr[i], map.get(arr[i]) + 1);
			}
			else
			{
				// Add new element
				map.put(arr[i], 1);
			}
		}
		System.out.println("  Occurrence ");
		//  Display calculated result
		for (int key: map.keySet())
		{
			System.out.println("  " + key + "  :  " + map.get(key));
		}
	}
	public static void main(String[] args)
	{
		// Array element
		int[] arr = {
			1 , 3 , 2 , 1 , 4 , 2 , 7 , 9 , 1 , 3 , 3 , 4 , 7
		};
		frequency(arr);
	}
}

Output

   1   3   2   1   4   2   7   9   1   3   3   4   7
  Occurrence
  1  :  3
  2  :  2
  3  :  3
  4  :  2
  7  :  2
  9  :  1