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How Can i Create a final class in C++?
i have tried by making constructors private . but i want to know an efficient way of doing this?

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Short answer: use the C++11 final specifier. It tells the compiler that a class may not be used as a base (or that a virtual function may not be overridden). Example:

class FinalClass final {
public:
    void doSomething();
};

struct Base { virtual void work(); };

struct Leaf final : Base {
    void work() override; // Leaf cannot be used as a base
};

Trying to derive from FinalClass (or override a final virtual function) gives a compile-time error.

Before C++11 there is no built-in keyword, so people used design/workaround patterns. already showed the factory/private-constructor approach; that works but changes object-creation semantics (no direct stack construction, extra friend/factory code). Other historical options were compiler-specific extensions (non-standard keywords) or access-control tricks that make deriving or instantiating awkward. ’s warning is worth repeating: think carefully why you want to forbid derivation — API design, performance hints, or security concerns are valid reasons, but “preventing users from experimenting” is not.

Recommendation: if the project can use C++11 or newer, mark classes or virtual functions final for intent and safety. It is clear, efficient, and enforced by compilers. For legacy code where C++11 is not an option, prefer explicit design and documentation or tightly scoped factory/friend patterns rather than brittle hacks. See the language reference for final for details and exact rules: final (cppreference).

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Member Avatar for Daishi

A final class? You mean like a final variable in Java? I haven't heard of that before in C++. But to answer your question about making private constructors, the only reason why I could see you doing something like that would be in this case:

class Something {
private:
	Something();

	static list<Something *> somethings;
public:
	static Something *New() {
		Something *something = new Something;
		somethings.push_back(something);
		return something;
	}
	//...
};

//  ...
//  In code somewhere

Something *something = Something::New();

That way you could possibly do a kind of memory management..not sure how that ties in with a 'final' class, though.

-Fredric

Member Avatar for Narue

>How Can i Create a final class in C++?
A "final" class in Java is a class that cannot be derived from, it's quite literally a concrete class that will never have subclasses. In C++ you basically can't do it without making the class harder to use. Are you doing this for the wrong reasons?

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