ActionListeners and main methods

Question

So I found a grid layout of a simple calculator somewhere that I thought could be fun to see if I could get working.

Problem is though, that after I started messing with it to add actionlisteners and such to the buttons, my console spewed following at me:

Error: Main method not found in class CalcMain.CalculatorMain, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

I'm still fairly new in coding, so I'm not entirely sure as to what this means, and how I should fix it.

The error popped up after I implemented ActionListener, and switched out

Calc.add(new JButton(buttons[i]));

with

test[i] = new JButton(buttons[i]);
test[i].addActionListener(this);
test[i].setActionCommand(buttons[i]);

What did I screw up, and what should I do to fix it? Any help is appreciated!

Thanks in advance!

public class CalculatorMain extends JFrame implements ActionListener {

private static final long serialVersionUID = 1L;

public CalculatorMain() {

    initUI();
}   

public final void initUI() {

    JPanel Calc = new JPanel();

    Calc.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    Calc.setLayout(new GridLayout(5, 4, 5, 5));

    String[] buttons = {
        "Cls", "Bck", "", "Close", "7", "8", "9", "/", "4",
        "5", "6", "*", "1", "2", "3", "-", "0", ".", "=", "+"
    };

    JButton[] test = new JButton[19];

    for (int i = 0; i < buttons.length; i++) {
        if (i == 2)
            Calc.add(new JLabel(buttons[i]));
        else
            test[i] = new JButton(buttons[i]);
            test[i].addActionListener(this);
            test[i].setActionCommand(buttons[i]);
    }

    add(Calc);

    setTitle("CalculatorDemo");
    setSize(350, 300);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);

    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            CalculatorMain demo = new CalculatorMain();
            demo.setVisible(true);
        }
    });
}

public void actionPerformed(ActionEvent e) {
    String name = e.getActionCommand();

    if(name.equals("1")) {
        System.out.println("No");
    }
    else if(name.equals("2")) {
        System.out.println("Yes");
    }
}
}