Common Elements in Two Arrays

public class CountCommonElements {

    public int[] solve(int[] A, int[] B) {

        //The maximum number of elements common can be min_length of A and B.
        int[] out = new int[Math.min(A.length, B.length)];

        //How many common elements?
        int count = 0;

        //Get frequency of all elements in first array in a HashMap
        Map<Integer, Integer> map = new HashMap<>();
        for(int i=0; i<A.length; i++){
            if(map.containsKey(A[i])){
                map.put(A[i], map.get(A[i])+1);
            }else{
                map.put(A[i], 1);
            }
        }

        //For each element in second array, check if it's present in the HashMap
        for(int i=0; i<B.length; i++){

            //If the element is present in the HashMap, reduce the frequency by 1, increase count and add it to temp array.
            if(map.containsKey(B[i])){

                int f = map.get(B[i]); //Frequency of B[i] in first array
                out[count] = B[i];
                count++;

                //If the frequency was 1, it was the last element in the first array, so remove it now. 
                if(f == 1){
                    map.remove(B[i]);
                }else{
                //If the frequency is more than 1, reduce it by 1.
                    map.put(B[i], (f-1));
                }
            }
        }

        //No common element.
        if(count == 0) return new int[]{};

        //The number of common elements is equal to count
        int[] arr = new int[count];
        for(int i=0; i<count; i++){
            arr[i] = out[i];
        }

        return arr;

    }
}