Java 字符统计：使用 Map 集合统计文件中的字母出现次数

import\ java.io.BufferedReader;import\ java.io.File;import\ java.io.FileReader;import\ java.io.IOException;import\ java.util.HashMap;import\ java.util.Map;public\ class\ Main\ {public\ static\ void\ main(String[]\ args)\ throws\ IOException\ {Map<Character,\ Integer>\ charCountMap\ =\ countCharacters("D:/calcCharNum.txt");printCharacterCount(charCountMap);}public\ static\ Map<Character,\ Integer>\ countCharacters(String\ filePath)\ throws\ IOException\ {Map<Character,\ Integer>\ charCountMap\ =\ new\ HashMap<>();File\ file\ =\ new\ File(filePath);BufferedReader\ br\ =\ new\ BufferedReader(new\ FileReader(file));String\ line;while\ ((line\ =\ br.readLine()) !=\ null) {for\ (char\ c\ :\ line.toCharArray()) {if\ (Character.isLetter(c)) {charCountMap.put(c,\ charCountMap.getOrDefault(c,\ 0) +\ 1);} } } br.close();return\ charCountMap;}public\ static\ void\ printCharacterCount(Map<Character,\ Integer>\ charCountMap) {StringBuilder\ sb\ =\ new\ StringBuilder();for\ (char\ c\ :\ charCountMap.keySet()) {sb.append(c).append("(").append(charCountMap.get(c)).append("),"); } sb.deleteCharAt(sb.length() -\ 1);System.out.println(sb.toString());}}