Add functionality to do calculations on the given GUI of calculator. My code is below:

package assignment8;

import java.awt.BorderLayout;

import java.awt.Font;

import java.awt.GridLayout;

import javax.swing.*;

public class Calculator {

public static final String[][] BUTTON_TEXTS = {

{"7", "8", "9", "+"},

{"4", "5", "6", "-"},

{"1", "2", "3", "*"},

{"0", ".", "=", "/"}

};

public static final Font BTN_FONT = new Font(Font.SANS_SERIF, Font.BOLD, 24);

private static void createAndShowGUI() {

JTextField field = new JTextField(15);

field.setFont(BTN_FONT.deriveFont(Font.PLAIN));

JPanel btnPanel = new JPanel(new GridLayout(BUTTON_TEXTS.length, BUTTON_TEXTS[0].length));

for (int i = 0; i

for (int j = 0; j

JButton btn = new JButton(BUTTON_TEXTS[i][j]);

btn.setFont(BTN_FONT);

btnPanel.add(btn);

}

}

JPanel mainPanel = new JPanel(new BorderLayout());

mainPanel.add(field, BorderLayout.PAGE_START);

mainPanel.add(btnPanel, BorderLayout.CENTER);

JFrame frame = new JFrame("Calculator");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.getContentPane().add(mainPanel);

frame.pack();

frame.setLocationRelativeTo(null);

frame.setVisible(true);

}

public static void main(String[] args) {

SwingUtilities.invokeLater(new Runnable() {

public void run() {

createAndShowGUI();

}

});

}

}

7 4 5 ?? 6 2 3