Programming Pandit

 Objective: Design a calculator using event-driven programming paradigm of Java with the following options.

                a) Decimal manipulations

                b) Scientific manipulations

Code:

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Calculator extends JFrame implements ActionListener {

    private JTextField display;

    private String currentInput = "";

    private double result = 0;

    private String operator = "";

    private boolean isScientific = false;

    public Calculator() {

        setTitle("Calculator");

        setSize(400, 500);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setLayout(new BorderLayout());

        

        display = new JTextField();

        display.setFont(new Font("Arial", Font.BOLD, 20));

        display.setHorizontalAlignment(JTextField.RIGHT);

        display.setEditable(false);

        add(display, BorderLayout.NORTH);

        

        JPanel panel = new JPanel();

        panel.setLayout(new GridLayout(5, 4, 5, 5));

        

        String[] buttons = {"7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", "0", ".", "=", "+", "C", "sin", "cos", "sqrt"};

        

        for (String text : buttons) {

            JButton button = new JButton(text);

            button.setFont(new Font("Arial", Font.BOLD, 18));

            button.addActionListener(this);

            panel.add(button);

        }

        

        add(panel, BorderLayout.CENTER);

    }

    

    @Override

    public void actionPerformed(ActionEvent e) {

        String command = e.getActionCommand();

        

        if (command.matches("[0-9.]")) {

            currentInput += command;

            display.setText(currentInput);

        } else if (command.matches("[+\\-*/]") || command.equals("sqrt")) {

            operator = command;

            result = Double.parseDouble(currentInput);

            currentInput = "";

        } else if (command.equals("=")) {

            double num = Double.parseDouble(currentInput);

            switch (operator) {

                case "+": result += num; break;

                case "-": result -= num; break;

                case "*": result *= num; break;

                case "/": result /= num; break;

                case "sqrt": result = Math.sqrt(result); break;

            }

            display.setText(String.valueOf(result));

            currentInput = "";

        } else if (command.equals("C")) {

            currentInput = "";

            result = 0;

            operator = "";

            display.setText("");

        } else if (command.equals("sin")) {

            result = Math.sin(Math.toRadians(Double.parseDouble(currentInput)));

            display.setText(String.valueOf(result));

        } else if (command.equals("cos")) {

            result = Math.cos(Math.toRadians(Double.parseDouble(currentInput)));

            display.setText(String.valueOf(result));

        }

    }

    

    public static void main(String[] args) {

        SwingUtilities.invokeLater(() -> {

            new Calculator().setVisible(true);

        });

    }

}

Output: