在没有对象的情况下调用构造函数

Question

我忘记在类名的前面添加对象名，但是代码仍在编译并且构造函数被调用。我真的很困惑这里实际发生了什么。这不是意味着我们可以在不创建对象的情况下调用构造函数吗？

我的代码：

#include<iostream>
using namespace std;

class PrintJobs
{
    private:
        int nPages;
        static int nTrayPages;
        static int nJobs;

    public:
        PrintJobs(int np) : nPages(np)
        {
            nJobs++;
            cout << "Printing " <<  nPages <<"pages" << endl;
        }
        ~PrintJobs()
        {
            --nJobs;
        }

        static int getJobs()
        {
            return nJobs;
        }

        static int checkPages()
        {
            return nTrayPages;
        }

        static void loadPages(int n)
        {
            nTrayPages += n ;
        }

};

int PrintJobs::nTrayPages = 500 ;
int PrintJobs::nJobs = 0 ;

int main()
{
    cout << "Jobs  " << PrintJobs::getJobs() << "\n" ;
    cout << "Pages " << PrintJobs::checkPages() << "\n";

    PrintJobs(10); /// This is the line I am confused about.

    cout << "Jobs  " << PrintJobs::getJobs() << "\n" ;
    cout << "Pages " << PrintJobs::checkPages() << "\n";
    {
        PrintJobs p(30) , p2(20);
        cout << "Jobs  " << PrintJobs::getJobs() << "\n" ;
            cout << "Pages " << PrintJobs::checkPages() << "\n";
            PrintJobs::loadPages(100);

    }

    cout << "Jobs  " << PrintJobs::getJobs() << "\n" ;
    cout << "Pages " << PrintJobs::checkPages() << "\n";
}

输出：

Jobs  0
Pages 500
Printing 10pages
Jobs  0
Pages 500
Printing 30pages
Printing 20pages
Jobs  2
Pages 500
Jobs  0
Pages 600