private static String appendVerticalBorder(String msg) {
    StringBuilder borderedMsgBuilder = new StringBuilder(msg.length() + 10);
    String[] lines = msg.split(SystemCompat.lineSeparator);
    for (int i = 0, N = lines.length; i < N; i++) {
      if (i != 0) {
        borderedMsgBuilder.append(SystemCompat.lineSeparator);
      }
      String line = lines[i];
      borderedMsgBuilder.append(VERTICAL_BORDER_CHAR).append(line);
    }
    return borderedMsgBuilder.toString();
  }
Add {@value #VERTICAL_BORDER_CHAR} to each line of msg.

@param msg the message to add border
@return the message with {@value #VERTICAL_BORDER_CHAR} in the start of each line
xlog/src/main/java/com/elvishew/xlog/formatter/border/DefaultBorderFormatter.java