import java.awt.; import java.awt.event.; import javax.swing.*;

class BuildCalculator extends JFrame implements ActionListener { JFrame actualWindow; JPanel resultPanel, buttonPanel, infoPanel; JTextField resultTxt; JButton btn_digits[] = new JButton[10]; JButton btn_plus, btn_minus, btn_mul, btn_div, btn_equal, btn_dot, btn_clear; char eventFrom; JLabel expression, appTitle, siteTitle; double oparand_1 = 0, operand_2 = 0; String operator = "=";

BuildCalculator() {
    Font txtFont = new Font("SansSerif", Font.BOLD, 20);
    Font titleFont = new Font("SansSerif", Font.BOLD, 30);
    Font expressionFont = new Font("SansSerif", Font.BOLD, 15);
    actualWindow = new JFrame("Calculator");
    resultPanel = new JPanel();
    buttonPanel = new JPanel();
    infoPanel = new JPanel();
    actualWindow.setLayout(new GridLayout(3, 1));
    buttonPanel.setLayout(new GridLayout(4, 4));
    infoPanel.setLayout(new GridLayout(3, 1));
    actualWindow.setResizable(false);
    appTitle = new JLabel("My Calculator");
    appTitle.setFont(titleFont);
    expression = new JLabel("Expression shown here");
    expression.setFont(expressionFont);
    siteTitle = new JLabel("www.btechsmartclass.com");
    siteTitle.setFont(expressionFont);
    siteTitle.setHorizontalAlignment(SwingConstants.CENTER);
    siteTitle.setForeground(Color.BLUE);
    resultTxt = new JTextField(15);
    resultTxt.setBorder(null);
    resultTxt.setPreferredSize(new Dimension(15, 50));
    resultTxt.setFont(txtFont);
    resultTxt.setHorizontalAlignment(SwingConstants.RIGHT);
    for (int i = 0; i < 10; i++) {
        btn_digits[i] = new JButton("" + i);
        btn_digits[i].addActionListener(this);
    }
    btn_plus = new JButton("+");
    btn_plus.addActionListener(this);
    btn_minus = new JButton("-");
    btn_minus.addActionListener(this);
    btn_mul = new JButton("*");
    btn_mul.addActionListener(this);
    btn_div = new JButton("/");
    btn_div.addActionListener(this);
    btn_dot = new JButton(".");
    btn_dot.addActionListener(this);
    btn_equal = new JButton("=");
    btn_equal.addActionListener(this);
    btn_clear = new JButton("Clear");
    btn_clear.addActionListener(this);
    resultPanel.add(appTitle);
    resultPanel.add(resultTxt);
    resultPanel.add(expression);
    for (int i = 0; i < 10; i++) {
        buttonPanel.add(btn_digits[i]);
    }
    buttonPanel.add(btn_plus);
    buttonPanel.add(btn_minus);
    buttonPanel.add(btn_mul);
    buttonPanel.add(btn_div);
    buttonPanel.add(btn_dot);
    buttonPanel.add(btn_equal);
    infoPanel.add(btn_clear);
    infoPanel.add(siteTitle);
    actualWindow.add(resultPanel);
    actualWindow.add(buttonPanel);
    actualWindow.add(infoPanel);
    actualWindow.setSize(300, 500);
    actualWindow.setVisible(true);
}

@Override
public void actionPerformed(ActionEvent e) {
    eventFrom = e.getActionCommand().charAt(0);
    String buildNumber;
    if (Character.isDigit(eventFrom)) {
        buildNumber = resultTxt.getText() + eventFrom;
        resultTxt.setText(buildNumber);
    } else if (e.getActionCommand() == ".") {
        buildNumber = resultTxt.getText() + eventFrom;
        resultTxt.setText(buildNumber);
    } else if (eventFrom != '=') {
        oparand_1 = Double.parseDouble(resultTxt.getText());
        operator = e.getActionCommand();
        expression.setText(oparand_1 + " " + operator);
        resultTxt.setText("");
    } else if (e.getActionCommand() == "Clear") {
        resultTxt.setText("");
    } else {
        operand_2 = Double.parseDouble(resultTxt.getText());
        expression.setText(expression.getText() + " " + operand_2);
        switch (operator) {
            case "+":
                resultTxt.setText("" + (oparand_1 + operand_2));
                break;
            case "-":
                resultTxt.setText("" + (oparand_1 - operand_2));
                break;
            case "*":
                resultTxt.setText("" + (oparand_1 * operand_2));
                break;
            case "/":
                try {
                    if (operand_2 == 0)
                        throw new ArithmeticException();
                    resultTxt.setText("" + (oparand_1 / operand_2));
                    break;
                } catch (ArithmeticException ae) {
                    JOptionPane.showMessageDialog(actualWindow, "Divisor can not be ZERO");
                }
        }
    }
}

}

class Main { public static void main(String[] args) { new BuildCalculator(); } }