find the frequency of elements in a java array

Question

I have an int array:

{1,2,4,2,3,5,6,4,3}

How can I find frequencies of array elements like 1=1,2=2,3=2,4=4... I need a class w

Answer 1

If range of the elements of the array is specified and limited to array size, the best solution is using hash map. T(n) = O(n), auxiliary space = O(n).

public static void findCount3(int[] a){
    Map hm = new HashMap();     
    for(int i = 0; i < a.length; i++){
            if(!hm.containsKey(a[i])){
               hm.put(a[i], 1);
            }else{
               hm.put(a[i], hm.get(a[i])+1);
    }               
    System.out.println(hm);         
}