U MAD, JAVA???

#include <iostream>
#include <stdexcept>

template<typename T>
class final
{
private:
    T data;
    bool used;

public:
    final(): used(false)
    {

    }
    final(const T &a)
    {
        used = true;
        data = a;
    }
    final(const final<T> &a)
    {
        used = true;
        data = a.get();
    }
    const T & operator=(const T &a)
    {
        if (used)
            throw std::runtime_error("Hey! I'm final!");
        else
        {
            used = true;
            data = a;
        }
        return data;
    }
    const final<T> & operator=(const final<T> &a)
    {
        if (used)
            throw std::runtime_error("Hey! I'm final!");
        else
        {
            used = true;
            data = a.get();
        }
        return *this;
    }
    const T & operator()() const
    {
        return data;
    }
};


int main()
{
    final<int> a;
    a = 5;
    std::cout << a();
    a = 7;
    std::cout << a();
    return 0;
}