Enissay

/////////////////
// Main class  //
/////////////////

package views;

// imports...

public class Main extends JFrame {
    // Main class with all variables and methods...
    //..........
    //..........

    public Main() {
        initComponents();
        createEvents(); // A method from the other class is called here like this:  Helpers.checkDataLine(line.trim());
                // Error: Cannot make a static reference to the non-static method checkDataLine(String) from the type Helpers
    }


    // Getters n Setters
    public JTextArea getTextAreaOuput() {
        return textAreaOuput;
    }

    public void setTextAreaOuput(JTextArea textAreaOuput) {
        this.textAreaOuput = textAreaOuput;
    }
}

//////////////////
// Helper class //
//////////////////
package views;

// imports...

public class Helpers {

    public void checkDataLine(String line) {
        try {   // it is a URL

            URL url = new URL(line);

        } catch (MalformedURLException e) { // it's not a URL

            // ERROR: Cannot make a static reference to the non-static method getTextAreaOuput() from the type Main
            Main.getTextAreaOuput().append("~~ [" + line + "] ~~ is NO URL ~~\n");
            searchText(line);

        }
    }

    public void searchText(String line) {
        Document doc;
        StringBuilder rootUrl = new StringBuilder("http://blah/");

        try {
            // Download the page
            doc = Jsoup.connect(rootUrl.append(line).toString()).get();

            Elements results = doc.select("a.match");

            for (Element element : results) {
                // ERROR: Cannot make a static reference to the non-static method getTextAreaOuput() from the type Main
                Main.getTextAreaOuput().append(element.text() + "\n");
            }


        } catch (IOException e) {
            // TODO: handle exception
        }

    }

}