public static ArrayList<WordInfo> countFrequency(String filename) {ArrayList<WordInfo> wordInfos=new ArrayList<>();Pattern pattern=Pattern.compile("[a-zA-Z]+-?[a-zA-Z]*");    //定义单词的正则表达式String text=Main.readFile(filename);    //调用readFile（）读取文本内容赋值给textif (text==null){return null;}Matcher matcher=pattern.matcher(text);  //利用之前定义的单词正则表达式匹配text中的单词String word;int index;WordInfo wordInfo;while(matcher.find()) {     //如果匹配到单词则进入循环处理word=matcher.group().toLowerCase();     //将匹配到的单词赋值给wordif (word.endsWith("-"))     //如果匹配到“单词-”情况，则去除符号“-”word=word.substring(0,word.length()-1);if ((index=Main.hasWord(wordInfos,word))!=-1) {     //如果动态数组wordInfos中已经有该单词，则将频数加一wordInfos.get(index).setFrequency(wordInfos.get(index).getFrequency()+1);}else{      //如果动态数组wordInfos中无该单词，则将该单词加入动态数组wordInfo=new WordInfo(word, 1);wordInfos.add(wordInfo);}}return wordInfos;}

Pattern pattern=Pattern.compile("[a-zA-Z]+-?[a-zA-Z]*");

String text=Main.readFile(filename); 

Matcher matcher=pattern.matcher(text);

while(matcher.find()) {   ......}

if (word.endsWith("-"))    word=word.substring(0,word.length()-1);

if ((index=Main.hasWord(wordInfos,word))!=-1) {     wordInfos.get(index).setFrequency(wordInfos.get(index).getFrequency()+1);}else{    wordInfo=new WordInfo(word, 1);wordInfos.add(wordInfo);}

 public static int hasWord(ArrayList<WordInfo> wordInfos, String word) {     //判断word是否存在于动态数组wordInfos中，若存在则返回位置，负责返回-1for (WordInfo wordInfo:wordInfos){if (wordInfo.getWord().equals(word.trim().toLowerCase()))return wordInfos.indexOf(wordInfo);}return -1;}

public static String readFile(String filename) {    //读取filename文本文件File file=new File(filename);StringBuilder sb = new StringBuilder();try {FileReader reader = new FileReader(file);BufferedReader br = new BufferedReader(reader);String str;while ((str = br.readLine()) != null) { //逐行读取文件内容，不读取换行符和末尾的空格sb.append(str + "\n");}br.close();return sb.toString();}catch (IOException e){System.out.println("读取文件失败！");}return null;}