Fast way to load all alphabetic characters to a hashmap

Use double brace initialization. It's very compact and helpful in initializing collections.

Map<String, Integer> map = new HashMap<String, Integer>() {
        {
            for (char ch = 'A'; ch <= 'Z'; ++ch) 
                put(String.valueOf(ch), 0); 
        }
};

Note that - put method is called without the map reference.

Do it in for loop:

for (char ch = 'A'; ch <= 'Z'; ++ch) 
  map.put(String.valueOf(ch), 0);