Valid Anagram

Given two strings s and t , write a function to determine if t is an anagram of s.

Example 1:

Input: s = "anagram", t = "nagaram"
Output: true

Example 2:

Input: s = "rat", t = "car"
Output: false

Note: You may assume the string contains only lowercase alphabets.

Follow up: What if the inputs contain unicode characters? How would you adapt your solution to such case?

class Solution {
    public boolean isAnagram(String s, String t) {
        HashMap<Character, Integer> map = new HashMap<>();
        for (int i = 0; i < s.length(); i++)
            if (!map.containsKey(s.charAt(i)))
                map.put(s.charAt(i), 1);
            else
                map.put(s.charAt(i), map.get(s.charAt(i)) + 1);
        for (int i = 0; i < t.length(); i++)
            if (!map.containsKey(t.charAt(i)))
                return false;
            else
                map.put(t.charAt(i), map.get(t.charAt(i)) - 1);
        for (char x : map.keySet())
            if (map.get(x) != 0)
                return false;
        return true;
    }
}