docs: protected void setAttachmentByExample(String example, Object att, String exp){
  		int p = getLastAcceptedState(example, 0);
  		if (p != -1){
  			this.attachments[p] = att;
  		}else{
  			// 说明精确匹配示范字符串有错误
  			throw new IllegalArgumentException("\"" + example + "\" can not match \"" + exp + "\"");
  		}
  	}