Group Anagrams

Given an array of strings, group anagrams together.

Input: ["eat", "tea", "tan", "ate", "nat", "bat"],
Output:
[
  ["ate","eat","tea"],
  ["nat","tan"],
  ["bat"]
]

Solution:

class Solution {
    public List<List<String>> groupAnagrams(String[] strs) {
        List<List<String>> result = new ArrayList<>();   
        if (strs == null || strs.length == 0) return result;
        Map<String, List<String>> map = new HashMap<>();
        for (String s : strs) {
            char[] arr = s.toCharArray();
            Arrays.sort(arr);
            String sorted = new String(arr);
            List<String> list = map.getOrDefault(sorted, new ArrayList<>());
            list.add(s);
            map.put(sorted, list);
        }
        for (Map.Entry<String, List<String>> entry : map.entrySet()) {
            result.add(entry.getValue());
        }
        return result;
    }
}