default constructor called instead of parameterized constructor

**the first constructor is supposed to take words from a txt file and the second one takes words from the string and add it to fileVec vector.

i'm trying to call a parameterized constructor but it doesn't work, instead it calls the default constructor **

#include <iostream>
#include <vector>
#include <fstream>
#include <sstream>
using namespace std;

class stringSet
{
private:
    int i = 0;
    string fileName, line, word, word2;
    istringstream iss;
    fstream file;
    vector<string> fileVec;

public:
    string str = "that's a string for parameterized constructor";

    stringSet()
    {
        cout << "Please enter filename: ";
        getline(std::cin, fileName);
        fileName += ".txt";
        file.open(fileName, ios::in);
        if (file.is_open())
        {
            while (getline(file, line))
            {
                iss.clear();
                iss.str(line);
                while (iss.good())
                {
                    iss >> word;
                    fileVec.push_back(word);
                    cout << fileVec[i] << endl;
                    i++;
                }
            }
        }
    }
    
    stringSet(string str)
    {
        istringstream iss2(str);
        while (iss2 >> word2)
            fileVec.push_back(word2);
        cout << fileVec[i] << endl;
        i++;
    }
};

int main()
{
    // stringSet();
    stringSet(str);
    return 0;
}

that code calls stringSet() instead of stringSet(str)