What is the problem here?
package com.codegym.task.task10.task1012;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
/*
Number of letters
*/
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
// Alphabet
String abc = "abcdefghijklmnopqrstuvwxyz";
char[] abcArray = abc.toCharArray();
ArrayList<Character> alphabet = new ArrayList<>();
for (char letter : abcArray) {
alphabet.add(letter);
}
// Read in strings
ArrayList<String> list = new ArrayList<>();
for (int i = 0; i < 10; i++) {
String s = reader.readLine();
list.add(s.toLowerCase());
}
HashMap<Character, Integer> letterMap = new HashMap<Character, Integer>();
for (Character letter: alphabet) {
letterMap.put(letter, 0);
}
for (String word: list) {
char[] chars = word.toCharArray();
for (Character letter: chars) {
letterMap.put(letter, letterMap.get(letter) + 1);
}
}
for (Character letter: alphabet) {
System.out.println(letter + " " + letterMap.get(letter));
}
}
}