import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Exec {
        public static void main(String[] args) {
                JFrame jf = new JFrame("My Window");
                jf.setLocation(100, 200);
                jf.setVisible(true);

                BorderLayout fl = new BorderLayout();
                jf.setLayout(fl);
                JTextField jtf = new JTextField();
                jtf.setHorizontalAlignment(JTextField.RIGHT);
                JPanel jp = new JPanel();
                jf.add(jtf, BorderLayout.NORTH);
                jf.add(jp, BorderLayout.CENTER);
                jp.setLayout(new GridLayout(4, 3));
                EHandling e = new EHandling(jtf);
                JButton[] array = new JButton[10];
                for (int i = 0; i < array.length; i++) {
                        array[i] = new JButton();
                        array[i].setText(String.valueOf(i));
                        jp.add(array[i]);
                        array[i].addActionListener(e);
                }
                JButton jb1 = new JButton();
                jb1.setText("+");
                JButton jb2 = new JButton();
                jb2.setText("=");
                jp.add(jb1);
                jp.add(jb2);
                jb1.setBackground(new Color(0, 255, 0));
                jb2.setBackground(Color.YELLOW);
                jf.pack();
                jb1.addActionListener(e);
                jb2.addActionListener(e);
        }
}

class EHandling implements ActionListener {
        JTextField jtf = null;
        int num1 = 0;

        public EHandling(JTextField jtf) {
                this.jtf = jtf;
        }

        public void actionPerformed(ActionEvent arg0) {
                JButton be = (JButton) arg0.getSource();

                if (be.getText().equals("+")) {
                        num1 = Integer.parseInt(jtf.getText());
                        jtf.setText("");
                } else if (be.getText().equals("=")) {
                        int num2 = Integer.parseInt(jtf.getText());
                        jtf.setText(String.valueOf(num1 + num2));
                } else {
                        jtf.setText(jtf.getText() + be.getText());
                }

        }

}