program 13 (calculator)

Question : Write a Java program to
create a simple calculator
using java AWT elements.
.Use a grid layout to
arrange buttons for the
digits and
basic operation +, -, /, *.
Add a text felid to display
the
results.


code:


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("SARVADNYA AWAGHAD D10A 05");
        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);
    }
    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");
                }
            }
        }
    }
}

public class Calculator {
    public static void main(String[] args) {

        new BuildCalculator();
    }
}