java.lang.Error exception generated on line number which has nothing (blank line) !!!

You are attempting to run non-compilable code currently. Instead, try to learn about the errors from the compiler, not the JVM. Compiler alerts you of the errors that a programmer shall resolve before trying to run the code, only after it compiles successfully.

In your code block, if you compile the program, the compiler will then inform you that using digits as an anonymous inner class's non-final local variable is prohibited. Declaring digits as the last variable is the solution. Revise the code as below to overcome the exception.

package Components;

import java.awt.event.*;
import java.awt.*;

import javax.swing.*;

public class Interface {


    public static void main(String[] args) {
        // TODO Auto-generated method stub

        JFrame frame;
        JPanel text = new JPanel();
        JPanel controlPanel = new JPanel();
        final JLabel digits = new JLabel ("");

        frame = new JFrame("Calculator");
        frame.setLayout(new FlowLayout());
        frame.setPreferredSize(new Dimension(300, 400));
        frame.addWindowListener(new WindowAdapter() {

            public void windowClosing(WindowEvent windowEvent) {
                System.exit(0);
            }
        });

        frame.add(text);
        frame.add(controlPanel);
        frame.setVisible(true);
        frame.pack();
//about where line 45 is

        digits.setBorder(BorderFactory.createLineBorder(Color.black));
        digits.setSize(new Dimension(30, 20));

        text.add(digits);

        JLabel greet = new JLabel("Welcome to Calculator!");
        greet.setSize(30, 20);
        greet.setVerticalAlignment(SwingConstants.TOP);
        greet.setBorder(BorderFactory.createLineBorder(Color.black));

        text.add(greet);
//about where line 60 is
        JButton one = new JButton("1");

        one.setSize(100, 30);

        one.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                digits.setText("1");
            }
        });
        controlPanel.add(one);
    }
}