import javax.swing.*;
import java.awt.*;
    public class Class {
        public static void main(String[] args) {
        JPanel windowContent;
        JTextField displayField;
        JButton button0 = null;
        JButton button1 = null;
        JButton button2 = null;
        JButton button3 = null;
        JButton button4 = null;
        JButton button5 = null;
        JButton button6 = null;
        JButton button7 = null;
        JButton button8 = null;
        JButton button9 = null;
        JButton buttonPoint;
        JButton buttonEqual;
        JPanel pl;
            Calculator() {
                windowContent = new JPanel();
                BorderLayout bl = new BorderLayout();
                windowContent.setLayout(bl);
                displayField = new JTextField(30);
                windowContent.add("North", displayField);

                button0 = new JButton("0");
                button0 = new JButton("1");
                button0 = new JButton("2");
                button0 = new JButton("3");
                button0 = new JButton("4");
                button0 = new JButton("5");
                button0 = new JButton("6");
                button0 = new JButton("7");
                button0 = new JButton("8");
                button0 = new JButton("9");
                buttonPoint = new JButton(".");
                buttonEqual = new JButton("=");
                    pl = new JPanel();
                    GridLayout gl = new GridLayout(4, 3);
                    pl.setLayout(gl);
                        pl.add(button1);
                        pl.add(button2);
                        pl.add(button3);
                        pl.add(button4);
                        pl.add(button5);
                        pl.add(button6);
                        pl.add(button7);
                        pl.add(button8);
                        pl.add(button9);
                        pl.add(button0);
                        pl.add(buttonPoint);
                        pl.add(buttonEqual);

                            windowContent.add("Center",pl);
                            JFrame frame = new JFrame("Calculator");
                            frame.setContentPane(windowContent);

                            frame.pack();
                            frame.setVisible(true);

            }
    }
    }```