Using FINAL with Data Member

最新推荐文章于 2025-12-06 09:52:47 发布
原创 最新推荐文章于 2025-12-06 09:52:47 发布 · 645 阅读 · 0 ·
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#constants #inheritance #variables #c++ #java #class

本文介绍了如何使用final关键字在Java和C++中定义常量。通过将final应用于变量，可以创建不可更改的命名常量。示例展示了在两种语言中定义ERRCODE常量的方法。
In addtion to the uses of final to prevent overridden or Inheritance, final can also be applied to variables to create what amounts to named constants. If you precede a class variable's name with final, its value cannot be  changed. below shows how to define a named constants in java and its same form in C++:
 
JAVA:    final int ERRCODE = 10;
C++:     const int ERRCODE = 10;
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是在这个类中查看版本么namespace OpenXLSX { constexpr const char * XLXmlDefaultVersion = "1.0"; constexpr const char * XLXmlDefaultEncoding = "UTF-8"; constexpr const bool XLXmlStandalone = true; constexpr const bool XLXmlNotStandalone = false; /** * @brief The XLXmlSavingDeclaration class encapsulates the properties of an XML saving declaration, * that can be used in calls to XLXmlData::getRawData to enforce specific settings */ class OPENXLSX_EXPORT XLXmlSavingDeclaration { public: // ===== PUBLIC MEMBER FUNCTIONS ===== // XLXmlSavingDeclaration() : m_version(XLXmlDefaultVersion), m_encoding(XLXmlDefaultEncoding), m_standalone(XLXmlNotStandalone) {} XLXmlSavingDeclaration(XLXmlSavingDeclaration const & other) = default; // copy constructor XLXmlSavingDeclaration(std::string version, std::string encoding, bool standalone = XLXmlNotStandalone) : m_version(version), m_encoding(encoding), m_standalone(standalone) {} ~XLXmlSavingDeclaration() {} /** * @brief: getter functions: version, encoding, standalone */ std::string const & version() const { return m_version; } std::string const & encoding() const { return m_encoding; } bool standalone_as_bool() const { return m_standalone; } std::string const standalone() const { return m_standalone ? "yes" : "no"; } private: // ===== PRIVATE MEMBER VARIABLES ===== // std::string m_version; std::string m_encoding; bool m_standalone; }; /** * @brief The XLXmlData class encapsulates the properties and behaviour of the .xml files in an .xlsx file zip * package. Objects of the XLXmlData type are intended to be stored centrally in an XLDocument object, from where * they can be retrieved by other objects that encapsulates the behaviour of Excel elements, such as XLWorkbook * and XLWorksheet. */ class OPENXLSX_EXPORT XLXmlData final { public: // ===== PUBLIC MEMBER FUNCTIONS ===== // /** * @brief Default constructor. All member variables are default constructed. Except for * the raw XML data, none of the member variables can be modified after construction. Hence, objects created * using the default constructor can only serve as null objects and targets for the move assignemnt operator. */ XLXmlData() = default; /** * @brief Constructor. 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The XLXmlData does not manage any dynamically allocated resources, so a default * destructor will suffice. */ ~XLXmlData(); /** * @brief check whether class is linked to a valid XML document * @return true if the class should have a link to valid data * @return false if accessing any other properties / methods could cause a segmentation fault */ bool valid() const { return m_xmlDoc != nullptr; } /** * @brief Copy constructor. The m_xmlDoc data member is a XMLDocument object, which is non-copyable. Hence, * the XLXmlData objects have a explicitly deleted copy constructor. * @param other */ XLXmlData(const XLXmlData& other) = delete; /** * @brief Move constructor. All data members are trivially movable. Hence an explicitly defaulted move * constructor is sufficient. * @param other */ XLXmlData(XLXmlData&& other) noexcept = default; /** * @brief Copy assignment operator. The m_xmlDoc data member is a XMLDocument object, which is non-copyable. * Hence, the XLXmlData objects have a explicitly deleted copy assignment operator. */ XLXmlData& operator=(const XLXmlData& other) = delete; /** * @brief Move assignment operator. All data members are trivially movable. Hence an explicitly defaulted move * constructor is sufficient. * @param other the XLXmlData object to be moved from. * @return A reference to the moved-to object. */ XLXmlData& operator=(XLXmlData&& other) noexcept = default; /** * @brief Set the raw data for the underlying XML document. Being able to set the XML data directly is useful * when creating a new file using a XML file template. E.g., when creating a new worksheet, the XML code for * a minimum viable XLWorksheet object can be added using this function. * @param data A std::string with the raw XML text. */ void setRawData(const std::string& data); /** * @brief Get the raw data for the underlying XML document. 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