I have class with main method like:

  public class Main {
        public static void main(String[] args) {
            long timeCheck;
            long periodOfTime;

             ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(2);

            long initialDelay = 0; // the time from now to delay execution
            long period = 1; // the period between successive executions 

            scheduler.scheduleAtFixedRate(new FeedReader(img, url, title, price), initialDelay, period, TimeUnit.DAYS);
            ...
            ...
        }
    }

and another class with some code:

public class FeedReader implements Runnable {

    private String img;
    private String url;
    private String title;
    private String price;

    public FeedReader(String img, String url, String title, String price) {
        this.img = img;
        this.url = url;
        this.title = title;
        this.price = price;

    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getImg() {
        return img;
    }

    public void setImg(String img) {
        this.img = img;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }

   ...

How to call properly via scheduleAtFixedRate method constructor with existing parameters from FeedReader class? I appreciate any help.

What have you tried? What errors do you get? The code you submitted doesn't seem to show much effort.

To run that code you need values for img, url etc. Where do those values come from? Eg: should the user type them in?

@JamesCherrill, thanks for interest in my question. So, I have two programms parser (FeedReader class) and another programm (with another logic) in parallel and Main class with main method.

  //  class with main method

public class Main {

public static void main(String[] args) {
    long timeCheck;
    long periodOfTime;

    // creation pool with 2 threads
    //A ScheduledExecutorService is capable of scheduling
    // tasks to run either periodically or once after a certain amount of time has elapsed.
    ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(2);

    long initialDelay = 0; // the time from now to delay execution 
    long period = 1; // the period between successive executions

    scheduler.scheduleAtFixedRate(new FeedReader(img, url, title, price), initialDelay, period, TimeUnit.DAYS);

    ...
    // some logic with another class
}

In main I need to call constructor which already has parameters. This is parser (class FeedReader):

public class FeedReader implements Runnable {

private String img;
private String url;
private String title;
private String price;

// constructor which I need to call from main
public FeedReader(String img, String url, String title, String price) {
    this.img = img;
    this.url = url;
    this.title = title;
    this.price = price;
   // feedAdd(img, url, title, price);
}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public String getUrl() {
    return url;
}

public void setUrl(String url) {
    this.url = url;
}

public String getImg() {
    return img;
}

public void setImg(String img) {
    this.img = img;
}

public String getPrice() {
    return price;
}

public void setPrice(String price) {
    this.price = price;
}

@Override
public String toString() {
    return "Article{" +
            "title='" + title + '\'' +
            ", url='" + url + '\'' +
            ", img='" + img + '\'' +
            ", price='" + price + "$" + '\'' +
            '}';
}

public void run() {
    try {
     // some logic to parse
    } catch (IOException e) {
        e.printStackTrace();
    }
}

// here method via feeAdd I'm adding info to database
 public String feedAdd(String img, String url, String title, String price) {

 // parameters that need to get from constructor
        this.img = img;
        this.url = url;
        this.title = title;
        this.price = price;

       // some logic  with connecting to db

long found = collection.count(Document.parse("title"));
        // check if feed exists or not
        if (found == 0) {
            Document doc = new Document("title", title)
                    .append("url", url)
                    .append("img", img)
                    .append("price", price);
            collection.insertOne(doc);
            mongoClient.close();
            System.out.println("Feed not exists in database. Written.");
            return "no_exists";
            // if feed exists
        } else {
            System.out.println("Feed exists in database.");
            mongoClient.close();
            return "exists";
        }
    }
}

Via FeedReader class I get info from website and I need to call parser from main via scheduleAtFixedRate line in main:

scheduler.scheduleAtFixedRate(new FeedReader(img, url, title, price), initialDelay, period, TimeUnit.DAYS);

But I can't do this, because IDE tells me to create again new fields with parameters here:
1.PNG

And I don't know how to call properly existing parameters and don't create new in main. I hope you understand me what I need.

I still can't see where you expect to get the initial values of img, url etc from. Is it from the // some logic to parse method? (if so, then the constructor is wrong and you don't need to pass in those parameters)

@JamesCherrill, in this place -> // some logic to parse, I have

public void run() {
    try {
 // creating list with articles
List<FeedReader> articleList = new ArrayList<>();
org.jsoup.nodes.Document doc = Jsoup.connect("weblink").get();
// here I'm parsing using variables
String img = ...
String url = ...
String title = ...
String price = ...
...
...
...

// here I'm adding variables that I parsed 
articleList.add(new FeedReader(img, url, title, price));

} catch (IOException e) {
        e.printStackTrace();
}

As I understand, when I'm writing this linearticleList.add(new FeedReader(img, url, title, price));, I'm getting my values that I need from constructor, no? Correct me, please.

What have you tried? What errors do you get? The code you submitted doesn't seem to show much effort.

Thanks for interesting too, @tinstaafl.

I tried to write constructor with parameters (which I used above in FeedReader) in another class Article like:

public class FeedReader implements Runnable {
    public void run() {
        try {
            List<Article> articleList = new ArrayList<>();
            org.jsoup.nodes.Document doc = Jsoup.connect("weblink").get();
            ...
            ...
            ...
            articleList.add(new Article(img, url, title, price));

    } catch (IOException e) {
        e.printStackTrace();
    }
}

// to add feed to db
public String feedAdd(String img, String url, String title, String price) {

  // some logic
    long found = collection.count(Document.parse("title"));
    // check if feed exists or not
    if (found == 0) {
        Document doc = new Document("title", title)
                .append("url", url)
                .append("img", img)
                .append("price", price);
        collection.insertOne(doc);
        mongoClient.close();
        System.out.println("Feed not exists in database. Written.");
        return "no_exists";
        // if feed exists
    } else {
        System.out.println("Feed exists in database.");
        mongoClient.close();
        return "exists";
    }
}

class Article {
    private String img;
    private String url;
    private String title;
    private String price;

    public Article(String img, String url, String title, String price) {
        this.img = img;
        this.url = url;
        this.title = title;
        this.price = price;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getImg() {
        return img;
    }

    public void setImg(String img) {
        this.img = img;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Article{" +
                "title='" + title + '\'' +
                ", url='" + url + '\'' +
                ", img='" + img + '\'' +
                ", price='" + price + "$" + '\'' +
                '}';
        }
    }
}

And call from main like:

   public class Main {
        public static void main(String[] args) {
        long timeCheck;
        long periodOfTime;

    // creation pool with 2 threads
    //A ScheduledExecutorService is capable of scheduling
    // tasks to run either periodically or once after a certain amount of time has elapsed.
    ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(2);

    long initialDelay = 0; // the time from now to delay execution
    long period = 1; // the period between successive executions
    scheduler.scheduleAtFixedRate(new FeedReader(), initialDelay, period, TimeUnit.DAYS);

    ...
    ...
  }
}

And the result is:
1.PNG

But in this way method public String feedAdd(String img, String url, String title, String price) from class FeedReader is never used:
3.PNG

I know that I can call feedAdd method directly from constructor like:

 public Article(String img, String url, String title, String price) {
            this.img = img;
            this.url = url;
            this.title = title;
            this.price = price;

      // added line
        feedAdd(String img, String url, String title, String price);
    }
    ...

In this case I didn't get nothing when input:

2.PNG

I don't think your problem is with code syntax, it's with the overall design/flow of the app.

Let's try to understand that... (stop me when I go wrong here)

You have a FeedReader class. An instance of that runs via a repeating scheduler to read some web info. When it finds the right info it creates an instance of Article - a class with variables like img, url etc - and adds it to a List.
There's a problem here because the List is a local variable that immediately goes out of scope and gets garbage collected.

You also have a method to add the same info to a database, but for some reason that does not use the Article instance that you created. Maybe that's the problem?

ps: all those set methods in Article are almost certainly a mistake. Why isn't Article immutable?

Thank you, James for trying to help. I solved by adding just one string. Anyway, I appreciate your help.

articleList.forEach(article -> feedAdd(article.getImg(), article.getTitle(), article.getUrl(), article.getPrice()));