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());
    }
}