代碼中有很多問題，基本上思路就是錯的。1，讀文件有問題，txt2String中System.lineSeparator()應該加s后面。2，分割字符串有問題，count函數(shù)str.split("b");未考慮其它分隔符的情況，正確的做法是用正則表達式str.split("\s");。3，初始化后，list.size()=0，當然不會進入循環(huán)。

如果只想要代碼的話看這里，java 字符串詞頻統(tǒng)計實例代碼
下面代碼是連接中的內(nèi)容

import java.util.ArrayList; 
import java.util.Collections; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 
 
public class WordsStatistics { 
 
    class Obj { 
        int count ; 
        Obj(int count){ 
            this.count = count; 
        } 
    } 
 
    public List<WordCount> statistics(String word) { 
        List<WordCount> rs = new ArrayList<WordCount>(); 
        Map <String,Obj> map = new HashMap<String,Obj>(); 
 
        if(word == null ) { 
            return null; 
        } 
        word = word.toLowerCase(); 
        word = word.replaceAll("'s", ""); 
        word = word.replaceAll(",", ""); 
        word = word.replaceAll("-", ""); 
        word = word.replaceAll("\\.", ""); 
        word = word.replaceAll("'", ""); 
        word = word.replaceAll(":", ""); 
        word = word.replaceAll("!", ""); 
        word = word.replaceAll("\n", ""); 
 
        String [] wordArray = word.split(" "); 
        for(String simpleWord : wordArray) { 
            simpleWord = simpleWord.trim();  
            if (simpleWord != null && !simpleWord.equalsIgnoreCase("")) { 
                Obj cnt = map.get(simpleWord); 
                if ( cnt!= null ) { 
                    cnt.count++; 
                }else { 
                    map.put(simpleWord, new Obj(1)); 
                } 
            } 
        } 
 
        for(String key : map.keySet()) { 
            WordCount wd = new WordCount(key,map.get(key).count); 
            rs.add(wd); 
        } 
 
        Collections.sort(rs, new java.util.Comparator<WordCount>(){ 
            @Override
            public int compare(WordCount o1, WordCount o2) { 
                int result = 0 ; 
                if (o1.getCount() > o2.getCount() ) { 
                    result = -1; 
                }else if (o1.getCount() < o2.getCount()) { 
                    result = 1; 
                }else { 
                    int strRs = o1.getWord().compareToIgnoreCase(o2.getWord()); 
                    if ( strRs > 0 ) { 
                        result = 1; 
                    }else { 
                        result = -1 ; 
                    } 
                } 
                return result; 
            } 
 
        }); 
        return rs; 
    } 
 
 
    public static void main(String args[]) { 
        String word = "Pinterest is might be aa ab aa ab marketer's dream  - ths site is largely used to curate products " ; 
        WordsStatistics s = new WordsStatistics(); 
        List<WordCount> rs = s.statistics(word); 
        for(WordCount word1 : rs) { 
            System.out.println(word1.getWord()+"*"+word1.getCount()); 
        } 
    } 
 
} 

后來自己又重新查了一下資料，重新寫了一下。
用map來存儲單詞和頻數(shù)顯然更加合理一些，用Comparator來做升降序排列。
這是老師給的一道實驗題，發(fā)一下題目吧，和我一樣的初學者有興趣也可以寫著試一試。
題目如下：

我把后來寫的代碼重新發(fā)一下。

代碼如下：

import java.io.*;
import java.io.FileReader;
import java.util.*;
import java.util.Map.Entry;

public class Counter {
    public static List<String> txt2String(File file) throws Exception{
        BufferedReader br = new BufferedReader(new FileReader("D:\\java eclipse\\eclipse-workspace\\Counter\\src\\news.txt"));    
        List<String> lists = new ArrayList<String>();  //存儲過濾后單詞的列表    
        String readLine = null;  
        while((readLine = br.readLine()) != null){    
            String[] wordsArr1 = readLine.split("[^a-zA-Z]");  //過濾出只含有字母的    
            for (String word : wordsArr1) {    
                if(word.length() != 0){  //去除長度為0的行    
                    lists.add(word);    
                }    
            }    
        }    
            
        br.close();    
        return lists;
    }
    
    public static void count(List<String> lists) {
         Map<String, Integer> wordsCount = new TreeMap<String,Integer>();  //存儲單詞計數(shù)信息，key值為單詞，value為單詞數(shù)         
         
            //單詞的詞頻統(tǒng)計    
            for (String li : lists) {    
                if(wordsCount.get(li) != null){    
                    wordsCount.put(li,wordsCount.get(li) + 1);    
                }else{    
                    wordsCount.put(li,1);    
                }    
        
            }
            ArrayList<Map.Entry<String,Integer>> list = new ArrayList<Map.Entry<String,Integer>>(wordsCount.entrySet());
            Collections.sort(list,new Comparator<Map.Entry<String,Integer>>(){    
                @Override    
                public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {    
                    return o2.getValue() - o1.getValue();  //降序    
                    //return o1.getValue() - o2.getValue();    //升序
                }    
            });
            //for(Map.Entry<String,Integer> m:wordsCount.entrySet()){
            //    System.out.println(m.getKey()+" "+m.getValue());
            //    }  
            for(int i = 0; i<list.size(); i++){    
                System.out.println(list.get(i).getKey()+ ": " +list.get(i).getValue());    
            }  
    }

    public static void main(String[] args) throws Exception{
        File file = new File("D:\\java eclipse\\eclipse-workspace\\Counter\\src\\news.txt");
        List<String> lists = new ArrayList<String>(txt2String(file));
        count(lists);
    }
}

運行結果如下：

如有錯誤，敬請指正。