1218.Longest arithmetic subsequence of given difference

class Solution {
    public int longestSubsequence(int[] arr, int d) {
       Map<Integer,Integer>mp=new HashMap<>();
       int max=0;
       for(int i=0;i<arr.length;i++){
        if(mp.containsKey(arr[i]-d)){
            mp.put(arr[i],mp.getOrDefault(arr[i]-d,0)+1);
        }
        else{
            mp.put(arr[i],1);
        }
        max=Math.max(max,mp.get(arr[i]));
       } 
       return max;
    }
}