在下面的java程序中添加按照字母顺序排序，如何添加

package test1;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main2 {
public static void main(String[] args) {
int count = 0;
File file = new File("F:\1.txt");
String s = "";
StringBuffer buffer = new StringBuffer();
try {
BufferedReader br = new BufferedReader(new FileReader(file));

        try {
            while ((s = br.readLine()) != null) {
                buffer.append(s + '\n');
            }
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }   
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    Pattern p = Pattern.compile("\\b[a-zA-Z]+\\b");
    Matcher m = p.matcher(buffer.toString());
    while(m.find()) {
        System.out.println(m.group());
        count ++ ;
    }
    System.out.println("总共：" + count + "个单词");
}

}

 对什么排序，是对单词排序么？
...
Comparator<String> comparator = new Comparator<String>(){  
   public int compare(String s1, String s2) {
     return s1.compareTo(s2);
     }
};
Matcher m = p.matcher(buffer.toString());
ArrayList<String> list = new ArrayList<String>();
while(m.find()) {
        list.add(m.group().toString());
        count ++ ;
    }
Collections.sort(list,comparator); 
for(String s: list)  
   System.out.println(s);  
 } 
 System.out.println("总共：" + count + "个单词");

String arr[] = {"HELLO", "WORLD", "good"};
// 按ascii码顺序排序 A~Z, a-z排序
Arrays.sort(arr);

java.util.Arrays 导入这个工具包