public GraphTrimmer(String graphDir, String outDir, File activeUsers,
			int maxUserFileSize) throws IOException {
		fileList = new File(graphDir).listFiles();
		buffArr = new byte[maxUserFileSize];
		this.outDir = outDir;
		set = new TreeSet<Long>();
		BufferedReader reader = new BufferedReader(new FileReader(activeUsers));
		String s;
		while ((s = reader.readLine()) != null) {
			set.add(Long.parseLong(s));
		}
		reader.close();
	}