java.java

import java.io.*;
import java.util.Hashtable;


public class LettersCounter {
    private static File file;
    private static BufferedReader reader;
    private static Hashtable<String, Integer> lettersFreq = new Hashtable<String, Integer>();

    public static void main(String[] args) {
        try {
            file = new File("text.txt");

            reader = new BufferedReader(new FileReader(file));
            String text;

            while ((text = reader.readLine()) != null) {
                int i;
                for (i = 0; i < text.length(); i++ ) {
                    String currentChar = String.valueOf(text.charAt(i)).toLowerCase();
                    if (currentChar.matches("[A-Za-z]+")) {
                        if (lettersFreq.get(currentChar) == null) {
                            lettersFreq.put(currentChar, 0);
                        }
                        lettersFreq.put(currentChar, lettersFreq.get(currentChar) + 1);
                    }
                }
            }

            System.out.println(lettersFreq);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

ruby.rb

file = File.open("text.txt", "r")

letterList = {}

while (line = file.gets)
  line.split('').each do |letter|
    letterList[letter] ||= 0
    letterList[letter] = letterList[letter] + 1
  end
end

puts letterList