Modernes C++ programmieren

//#(compile) c++; compiler:g132; options:-O3 -std=c++23; libs:-
// https://godbolt.org/z/n4e8xdEGj 
#include <iostream> // cout
#include <string>
using std::string;
class Tree {
    static size_t countConstructed_;
    static size_t countDestructed_;
    string kind_;
    Tree(string kind) : kind_{kind}      // private constructor
        { ++countConstructed_; }
public:
    Tree(const Tree& o) : kind_{o.kind_}
        { ++countConstructed_; }
    string getKind() const { return kind_; }
    ~Tree() { ++countDestructed_; }
    static Tree create(string kind) { return Tree{kind}; }
    static void stats(std::ostream& os) {
        os << "Constructed:+" << countConstructed_
           << " Destructed:-" << countDestructed_ << "\n";
    }
};
size_t Tree::countConstructed_ = 0;
size_t Tree::countDestructed_ = 0;
int main() {
    Tree birch = Tree::create("Birch");
    for(auto kind : {"Ash", "Yew", "Oak"}) {
        Tree temp = Tree::create(kind);
        std::cout << temp.getKind() << "\n";
    }
    Tree::stats(std::cout);
}