Java版统计文件中的每个单词出现次数

正则表达式之Pattern和Matcher，请参见转载博客    http://www.cnblogs.com/haodawang/p/5967219.html

代码实现：

 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeMap;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 public class CountWorks {
     public static void main(String[] args) {
         BufferedReader br = null;
         try {
             br = new BufferedReader(new FileReader("short.txt"));
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         }
         StringBuffer sb1 = new StringBuffer();
         String line = null;
         try {
             while((line = br.readLine()) != null) {
                 sb1 = sb1.append(line);
             }
         } catch (IOException e) {
             e.printStackTrace();
         }
         try {
             br.close();
         } catch (IOException e1) {
             e1.printStackTrace();
         }
         String sb=sb1.toString().toLowerCase();
         Pattern pattern = Pattern.compile("[a-zA-Z']+");//a 到 z 或 A 到 Z，两头的字母包括在内（范围）
         Matcher matcher = pattern.matcher(sb);
         Map<String, Integer> map = new TreeMap<String, Integer>();
         String word = "";
         Integer num = null;
         int total = 0;

         while(matcher.find()) {
             word = matcher.group();
             total ++;
             if(map.containsKey(word)) {
                 num = map.get(word);//get(),返回指定键值所映射的值，取出map中word单词的个数
                 num += 1;
             } else {
                 num = 1;
             }
             map.put(word, num);
         }
         Set<String> keys = map.keySet();
         for (String key : keys) {
             Integer value = map.get(key);
             System.out.printf("%s: %s\n", key, value);
         }
         System.out.println();
         System.out.println("total words : " + total);
         System.out.println("different words : " + map.size());
     }
 }