java上机

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<String, Integer> map = new TreeMap<String, Integer>();
        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<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(
                map.entrySet());
        /*
         * 重写比较器
         * 取出单词个数（value）比较
         */
        Comparator<Map.Entry<String, Integer>> comparator = new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Map.Entry<String, Integer> left,
                    Map.Entry<String, Integer> 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);
        }
    }
}