Shortest Word Distance

Given a list of words and two words word1 and word2, return the shortest distance between these two words in the list.
For example,
Assume that words = ["practice", "makes", "perfect", "coding", "makes"].
Given word1 = “coding”, word2 = “practice”, return 3.
Given word1 = "makes", word2 = "coding", return 1.
Note:
You may assume that word1 does not equal to word2, and word1 and word2 are both in the list.

public class Solution {
    public int shortestDistance(String[] words, String word1, String word2) {
        HashMap<String, List<Integer>> map = new HashMap<String, List<Integer>>();
        for (int i = 0; i < words.length; i++) {
            String word = words[i];
            List<Integer> arr = map.get(word);
            if (arr == null) {
                arr = new ArrayList<Integer>();
                map.put(word, arr);
            }
            arr.add(i);
        }
        int dis = words.length;
        List<Integer> arr1 = map.get(word1);
        List<Integer> arr2 = map.get(word2);
        for (int a1 : arr1) {
            for (int a2 : arr2) {
                dis = Math.min(dis, Math.abs(a1 - a2));
            }
        }
        return dis;
    }
}

====

public class Solution {
    public int shortestDistance(String[] words, String word1, String word2) {
        int p1 = -1;
        int p2 = -1;
        int res = words.length;
        for (int i = 0; i < words.length; i++) {
            String word = words[i];
            if (word.equals(word1)) {
                p1 = i;
            }
            if (word.equals(word2)) {
                p2 = i;
            }
            if (p1 != -1 && p2 != -1) {
                res = Math.min(res, Math.abs(p1 - p2));
            }
        }
        return res;
    }
}