基本思路：用hashmap儲存key值為單詞，value為單詞出現的頻率。

1. hashmap儲存對單詞的遍歷
2. map的遍歷儲存在set中
3. 排序 TreeSet
4. 對wordEntity實現comparable介面重寫compareTo（）和toString（）
5. 增序為cmp的值，降序課為-cmp的值

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import
 
 java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.TreeSet;


public class wordCen {
    public static void main(String args[]){
        System.out.println("請輸入檔案的地址");
        Scanner in
 
=new Scanner(System.in);
        String Filepath=in.next();
        File file=new File(Filepath);
        String buffer;
        Map<String,Integer> map=new HashMap<String,Integer>();
        try {
            BufferedReader reader=new BufferedReader(new FileReader(file));
             while
 
((buffer=reader.readLine())!=null){
             StringTokenizer st = new StringTokenizer(buffer, ", !’");
             while(st.hasMoreTokens()){
                 String str=st.nextToken();
                 if(map.containsKey(str)) map.put(str, map.get(str)+1);
                 else map.put(str, 1);
             }
             }

             Set<WordEntity> set=new TreeSet<WordEntity>();
             for(String s:map.keySet()){
                 WordEntity wordEntry=new WordEntity(s,map.get(s));
                 set.add(wordEntry);     
             }

             Iterator<WordEntity>  ite=set.iterator();
             int count=0;
             while(ite.hasNext()){
                // String wr=ite.next();
                 if(count>=10) break;
                 System.out.println(ite.next());
                 count++;

             }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            System.out.println("檔案沒有找到");
        }
        catch(IOException e){
            System.out.println("檔案讀異常");    
        }

    }
}

wordEntity類的實現：

public class WordEntity implements Comparable<WordEntity>{
private String word;
private Integer count;
public WordEntity(String key, Integer value) {
    super();
    this.word = key;
    this.count = value;
}
public String getKey() {
    return word;
}
public Integer getValue() {
    return count;
}
public void setKey(String key) {
    this.word = key;
}
public void setValue(Integer value) {
    this.count = value;
}
@Override
public String toString() {
    return "WordEntity key=" + word + ", 出現的次數" + count ;
}
@Override
public int compareTo(WordEntity O) {
    // TODO Auto-generated method stub
    int cmp=count.intValue()-O.count.intValue();
    return (cmp==0?word.compareTo(O.getKey()):-cmp);
}

}