code: @Override
  	public String toJSONString(int indentFactor) throws JSONException {
  		final StringWriter w = new StringWriter();
  		return this.write(w, indentFactor, 0).toString();
  	}
docs: 格式化输出JSON字符串
  
  @param indentFactor 每层缩进空格数
  @return JSON字符串
  @throws JSONException 包含非法数抛出此异常