检查两个String是否为anagram

Question

I wrote a method for checking whether two Strings are anagram or not. The method is returning true even if the words are not anagram. I don't see any bug in the code, any ideas how can I improve ? The method is as following,

public static boolean checkAnagram( String one, String two){

    if ( one.length() != two.length() ) 
        return false;

    char[] letters  = new char[128];

    for ( char c: one.toCharArray()){

        letters[c]++;
    } 


    for( int j =0; j < two.length(); j++){

        int c = (int) two.charAt(j);

        if( --letters[c] < 0) return false;

    }

    return true;
}

Answer 1

letters is a char array, so letters[i] can never be negative (the range of char is 0 to 2^16-1 ). If you try to decrement it below 0, it will underflow to Character.MAX_VALUE . Change it to an int[] .

Answer 2

In the first for loop you are using:

letters[c]++;

when c is a char .
In the other for loop you cast c to int by performing (int)two.charAt(j) before assigning it to c .

Also, you are getting true each time because you can't have a negative value in a char array, so at every index exists that letters[index] >= 0 . You need to change the array to int[128] .