valid_anagram.java

public class Solution {
    // only for ASCII characters which takes one byte in storage
    public boolean isAnagram(String s, String t) {
        if(s == null && t == null)
            return true;
        if(s == null && t != null)
            return false;
        if(s != null && t == null)
            return false;
        if(s.length() != t.length())
            return false;
        int[] counts1 = new int[256];
        int[] counts2 = new int[256];
        parse(counts1, s);
        parse(counts2, t);
        for(int i=0; i<256; i++)
            if(counts1[i] != counts2[i])
                return false;
        return true;
    }
    
    private void parse(int[] arr, String s) {
        for(char c : s.toCharArray())
            arr[c] += 1;
    }
}