根据行号截取读取文本文件

FileUtils.java

public static String readStr(String filepath, int startLine) {
        File file = new File(filepath);
        if (!file.exists()) return "";
        startLine = Math.max(startLine, 1);
        LineNumberReader reader = null;
        StringBuilder sb = new StringBuilder();
        String line;
        try {
            reader = new LineNumberReader(new FileReader(file));
            while ((line = reader.readLine()) != null) {
                if (reader.getLineNumber() >= startLine) {
                    if (reader.getLineNumber() > startLine) {
                        sb.append("\n");
                    }
                    sb.append(line);
                }
            }
            return sb.toString();
        } catch (IOException e) {
            MyLog.e(TAG, "写文件失败:" + filepath, e);
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return "";
    }