Group Anagrams LeetCode solution in Java

1
class Solution {
2
  public List<List<String>> groupAnagrams(String[] strs) {
3
    HashMap<String, ArrayList<String>> hm = new HashMap<>();
4
    for (String s : strs) {
5
      char ch[] = s.toCharArray();
6
      Arrays.sort(ch);
7
      StringBuilder sb = new StringBuilder("");
8
      for (char c : ch) {
9
        sb.append(c);
10
      }
11
      String str = sb.toString();
12
      if (hm.containsKey(str)) {
13
        ArrayList<String> temp = hm.get(str);
14
        temp.add(s);
15
        hm.put(str, temp);
16
      } else {
17
        ArrayList<String> temp = new ArrayList<>();
18
        temp.add(s);
19
        hm.put(str, temp);
20
      }
21
    }
22
    System.out.println(hm);
23
    List<List<String>> res = new ArrayList<>();
24
    for (ArrayList<String> arr : hm.values()) {
25
      res.add(arr);
26
    }
27
    return res;
28
  }
29
}