Java统计文档中英文单词个数

public class CountWords {
	public static void main(String[] args) {
		BufferedReader br = null;
		try {
			br = new BufferedReader(new FileReader("english.txt"));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
		StringBuffer sb = new StringBuffer();
		String line = null;
		try {
			while((line = br.readLine()) != null) {
				sb = sb.append(line);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		try {
			br.close();
		} catch (IOException e1) {
			e1.printStackTrace();
		}
		
		Pattern pattern = Pattern.compile("[a-zA-Z']+");
		Matcher matcher = pattern.matcher(sb);
		Map<String, Integer> map = new HashMap<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);
				num += 1;
			} else {
				num = 1;
			}
			map.put(word, num);
		}
		
		PrintWriter pw = null;
		try {
			pw = new PrintWriter(new FileWriter("result.txt"), true);
		} catch (IOException e) {
			e.printStackTrace();
		}
		Iterator<String> iterator = map.keySet().iterator();
		while(iterator.hasNext()) {
			String tmp = iterator.next();
			pw.println(tmp  + " : " + map.get(tmp));
		}
		pw.println("total words : " + total);
		pw.println("different words : " + map.size());
		pw.close();

	}
}