Leetcode: Ransom Note

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.

Each letter in the magazine string can only be used once in your ransom note.

Note:
You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true

using one array

public class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        int[] mLetters = new int[26];
        for (int i=0; i<magazine.length(); i++) {
            mLetters[magazine.charAt(i) - 'a']++;
        }
        for (int j=0; j<ransomNote.length(); j++) {
            if (mLetters[ransomNote.charAt(j) - 'a']-- == 0) return false;
        }
        return true;
    }
}