[완료] 자바 코드 분석하다가 막혀서 질문드립니다...

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.BufferedReader;
 
class Cleaner{
    public static void main(String a[]) {
        String source = readFile("source.java");
        System.out.println(source.replaceAll("(?:/\\*(?:[^*]|(?:\\*+[^*/]))*\\*+/)|(?://.*)", ""));
    }
 
    static String readFile(String fileName) {
        File file = new File(fileName);
        char[] buffer = null;
        try {
            BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
            buffer = new char[(int) file.length()];
            int i = 0;
            int c = bufferedReader.read();
            while (c != -1) {
                buffer[i++] = (char) c;
                c = bufferedReader.read();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new String(buffer);
    }
}