Find the longest subarray with distinct entries

LongestSubarrayWithDistinctEntries.java

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/*
   Problem: Write a program that takes an array and returns the length of the longest
   subarray with the
   property that that all its elements are distinct
   Ex. {f,s,f,e,t,w,e,n,w,e} then longest subarray without duplicate is {s,f,e,t,w}
   Solution:- Maintain a map of character to when that character was last appeared
   Every time you add a new entry check if that entry has appeared before if yes
   get its index, check if that index is greater than longestDuplicateFreeSubarrayStartIndex
   if yes calculate distance between i - longestDuplicateFreeSubarrayStartIndex, check if thats max

    */
public class LongestSubarrayWithDistinctEntries {

    public int longestSubarrayWithDistinctEntries(List<Character> A) {
        Map<Character, Integer> mostRecentOccurance = new HashMap<>();
        int longestDuplicateFreeSubarrayStartIndex = 0;
        int result = 0;
        for (int i = 0; i < A.size(); i++) {
            Integer dupIdIdx = mostRecentOccurance.put(A.get(i), i);
            if (dupIdIdx != null) {
                if (dupIdIdx > longestDuplicateFreeSubarrayStartIndex) {
                    result = Math.max(result, i - longestDuplicateFreeSubarrayStartIndex);
                    longestDuplicateFreeSubarrayStartIndex = dupIdIdx + 1;
                }
            }
        }
        result = Math.max(result, A.size() - longestDuplicateFreeSubarrayStartIndex);
        return result;
    }
}