package wordcont;import java.io.BufferedReader;import java.io.FileReader;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.List;import java.util.Map;import java.util.TreeMap;import java.util.regex.Matcher;import java.util.regex.Pattern;public class wordcont {    public static void main(String[] args) throws Exception     {        BufferedReader reader = new BufferedReader(new FileReader("D://123.txt"));        StringBuffer buffer = new StringBuffer();        String line = null;        while ((line = reader.readLine()) != null) {            buffer.append(line);        }        reader.close();        Pattern expression = Pattern.compile("[a-zA-Z]+");// 定义正则表达式匹配单词        String string = buffer.toString();        Matcher matcher = expression.matcher(string);//        Map
     
       map = new TreeMap
      
       ();        String word = "";        int times = 0;        while (matcher.find()) {// 是否匹配单词            word = matcher.group();// 得到一个单词-树映射的键            if (map.containsKey(word)) {// 如果包含该键，单词出现过                times = map.get(word);// 得到单词出现的次数                map.put(word, times + 1);            } else {                map.put(word, 1);// 否则单词第一次出现，添加到映射中            } }        /*         * 核心：如何按照TreeMap 的value排序而不是key排序.将Map.Entry放在集合里， 重写比较器，在用         * Collections.sort(list, comparator);进行 排序         */         List
       
        
         > list = new ArrayList
         
          
           >( map.entrySet()); /* * 重写比较器 * 取出单词个数（value）比较 */ Comparator
           
            
             > comparator = new Comparator
             
              
               >() { public int compare(Map.Entry
               
                 left, Map.Entry
                
                  right) { return (left.getValue()).compareTo(right.getValue()); } }; Collections.sort(list, comparator);// 排序 // 打印最多五个 int last = list.size() - 1; for (int i = last; i > last - 6; i--) { String key = list.get(i).getKey(); Integer value = list.get(i).getValue(); System.out.println(key + " :" + value); } }}