TemperatureConverter/TemperatureConverterGUI.java at main · adeeljameel810-byte/TemperatureConverter · GitHub

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package com.tempconverter;

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

/**
 * GUI for the temperature converter.
 * Demonstrates Inheritance (extends JFrame) and Encapsulation.
 */
public class TemperatureConverterGUI extends JFrame {
    // Encapsulated components
    private JTextField inputField;
    private JComboBox<String> fromUnitBox;
    private JComboBox<String> toUnitBox;
    private JButton convertButton;
    private JTextField outputField;
    private TemperatureConverter converter;
    private Border defaultInputBorder;

    public TemperatureConverterGUI() {
        converter = new TemperatureConverter();
        initializeComponents();
        setupLayout();
        addListeners();
        setAppearance();
    }

    private void initializeComponents() {
        inputField = new JTextField(10);
        defaultInputBorder = inputField.getBorder();
        fromUnitBox = new JComboBox<>(new String[]{"Celsius", "Fahrenheit", "Kelvin"});
        toUnitBox = new JComboBox<>(new String[]{"Celsius", "Fahrenheit", "Kelvin"});
        convertButton = new JButton("Convert");
        outputField = new JTextField(10);
        outputField.setEditable(false);
    }

    private void setupLayout() {
        setTitle("Temperature Converter");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(10, 10, 10, 10);

        gbc.gridx = 0; gbc.gridy = 0;
        add(new JLabel("Input Temperature:"), gbc);

        gbc.gridx = 1;
        add(inputField, gbc);

        gbc.gridx = 2;
        add(fromUnitBox, gbc);

        gbc.gridx = 0; gbc.gridy = 1;
        add(new JLabel("Convert to:"), gbc);

        gbc.gridx = 1;
        add(toUnitBox, gbc);

        gbc.gridx = 1; gbc.gridy = 2;
        add(convertButton, gbc);

        gbc.gridx = 0; gbc.gridy = 3;
        add(new JLabel("Result:"), gbc);

        gbc.gridx = 1;
        add(outputField, gbc);

        pack();
        setLocationRelativeTo(null);
    }

    private void addListeners() {
        convertButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String inputText = inputField.getText().trim();
                if (inputText.isEmpty()) {
                    inputField.setBorder(BorderFactory.createLineBorder(Color.RED));
                    JOptionPane.showMessageDialog(TemperatureConverterGUI.this, "Input temperature is required.", "Input Error", JOptionPane.ERROR_MESSAGE);
                    return;
                }

                double value;
                try {
                    value = Double.parseDouble(inputText);
                } catch (NumberFormatException ex) {
                    inputField.setBorder(BorderFactory.createLineBorder(Color.RED));
                    JOptionPane.showMessageDialog(TemperatureConverterGUI.this, "Please enter a valid number (e.g., 36.6 or -10).", "Input Error", JOptionPane.ERROR_MESSAGE);
                    return;
                }

                String fromUnit = (String) fromUnitBox.getSelectedItem();
                String toUnit = (String) toUnitBox.getSelectedItem();

                // Physical validation: do not allow values below absolute zero
                if ("Kelvin".equals(fromUnit) && value < 0) {
                    inputField.setBorder(BorderFactory.createLineBorder(Color.RED));
                    JOptionPane.showMessageDialog(TemperatureConverterGUI.this, "Kelvin cannot be negative. Absolute zero is 0 K.", "Input Error", JOptionPane.ERROR_MESSAGE);
                    return;
                }
                if ("Celsius".equals(fromUnit) && value < -273.15) {
                    inputField.setBorder(BorderFactory.createLineBorder(Color.RED));
                    JOptionPane.showMessageDialog(TemperatureConverterGUI.this, "Temperature cannot be below absolute zero (-273.15 °C).", "Input Error", JOptionPane.ERROR_MESSAGE);
                    return;
                }
                if ("Fahrenheit".equals(fromUnit) && value < -459.67) {
                    inputField.setBorder(BorderFactory.createLineBorder(Color.RED));
                    JOptionPane.showMessageDialog(TemperatureConverterGUI.this, "Temperature cannot be below absolute zero (-459.67 °F).", "Input Error", JOptionPane.ERROR_MESSAGE);
                    return;
                }

                // Reset any previous error styling
                inputField.setBorder(defaultInputBorder);

                double result = converter.convert(value, fromUnit, toUnit);
                outputField.setText(String.format("%.2f", result));
            }
        });
    }

    private void setAppearance() {
        // Make it attractive
        getContentPane().setBackground(new Color(240, 248, 255)); // Alice blue
        convertButton.setBackground(new Color(70, 130, 180)); // Steel blue
        convertButton.setForeground(Color.WHITE);
        convertButton.setFocusPainted(false);
        Font font = new Font("Arial", Font.PLAIN, 14);
        inputField.setFont(font);
        outputField.setFont(font);
        fromUnitBox.setFont(font);
        toUnitBox.setFont(font);
        convertButton.setFont(font);
    }
}