javalab/P9.java

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

public class P9 extends JFrame {
    private JTextField displayField;

    public P9() {
        setTitle("Scientific Calculator");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(true);

        displayField = new JTextField();
        displayField.setPreferredSize(new Dimension(300, 30));
        displayField.setEditable(false);

        JPanel buttonPanel = new JPanel(new GridLayout(6, 4, 10, 10));

        String[] buttonLabels = {
                "7", "8", "9", "/",
                "4", "5", "6", "*",
                "1", "2", "3", "-",
                "0", ".", "=", "+",
                "sin", "cos", "tan", "sqrt",
                "e", "^", "pi", "clr"
        };

        for (String label : buttonLabels) {
            JButton button = new JButton(label);
            button.addActionListener(new ButtonClickListener());
            buttonPanel.add(button);
        }

        setLayout(new FlowLayout());
        add(displayField);
        add(buttonPanel);

        pack();
        setLocationRelativeTo(null);
        setVisible(true);
    }

    private class ButtonClickListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            String command = event.getActionCommand();
            String expression = displayField.getText();
            if ("=".equals(command)) {
                calculate();
            } else if ("clr".equals(command)) {
                displayField.setText("");
            } else if ("sin".equals(command)) {
                displayField.setText(String.valueOf(Math.sin(Double.parseDouble(expression))));
            } else if ("cos".equals(command)) {
                displayField.setText(String.valueOf(Math.cos(Double.parseDouble(expression))));
            } else if ("tan".equals(command)) {
                displayField.setText(String.valueOf(Math.tan(Double.parseDouble(expression))));
            } else if ("sqrt".equals(command)) {
                displayField.setText(String.valueOf(Math.sqrt(Double.parseDouble(expression))));
            } else {
                displayField.setText(displayField.getText() + command);
            }
        }

        private void calculate() {
            String expression = displayField.getText();
            try {
                double result = evaluateExpression(expression);
                displayField.setText(String.valueOf(result));
            } catch (NumberFormatException e) {
                displayField.setText("Error");
            }
        }

        private double evaluateExpression(String expression) {
            return new Object() {
                int pos = -1, ch;

                void nextChar() {
                    ch = (++pos < expression.length()) ? expression.charAt(pos) : -1;
                }

                boolean eat(int charToEat) {
                    while (ch == ' ') nextChar();
                    if (ch == charToEat) {
                        nextChar();
                        return true;
                    }

                    return false;
                }

                double parse() {
                    nextChar();
                    double x = parseExpression();
                    if (pos < expression.length()) throw new RuntimeException("Unexpected character: " + (char) ch);
                    return x;
                }

                double parseExpression() {
                    double x = parseTerm();
                    while(true) {
                        if (eat('+')) x += parseTerm();
                        else if (eat('-')) x -= parseTerm();
                        else return x;
                    }
                }

                double parseTerm() {
                    double x = parseFactor();
                    while (true) {
                        if (eat('*')) x *= parseFactor();
                        else if (eat('/')) x /= parseFactor();
                        else return x;
                    }
                }

                double parseFactor() {
                    if (eat('+')) return parseFactor();
                    if (eat('-')) return -parseFactor();

                    double x;
                    int startPos = this.pos;
                    if (eat('(')) {
                        x = parseExpression();
                        eat(')');
                    } else if ((ch >= '0' && ch <= '9') || ch == '.') {
                        while ((ch >= '0' && ch <= '9') || ch == '.') nextChar();
                        x = Double.parseDouble(expression.substring(startPos, this.pos));
                    } else if (eat('e')) {
                        x = Math.E;
                    } else if (eat('p')) {
                        eat('i');
                        x = Math.PI;
                    } else {
                        throw new RuntimeException("Unexpected character: " + (char) ch);
                    }

                    if (eat('^')) x = Math.pow(x, parseFactor());

                    return x;
                }
            }.parse();
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new P9();
            }
        });
    }
}