Create a Calendar Generator Using Java swing

How to Create a Calendar Generator Using Java swing

Discover how to create a calendar generator using Java Swing with step-by-step instructions and complete source code. This tutorial guides you in building a functional application that generates calendars for specific months or years, highlights the current date, and features a custom, modern GUI with a gradient background.

1. Backend Logic

The backend logic handles the core functionality of generating the calendar, including leap year calculations, determining the number of days in a month, and calculating the day of the week for the first day of the month.

Leap Year Calculation

The isLeapYear method checks whether a given year is a leap year. A leap year is divisible by 4, but not by 100 unless it’s also divisible by 400. This logic ensures accurate leap year detection.

Days in a Month

The getDaysInMonth method determines the number of days in a given month and year. It accounts for February’s variability (28 or 29 days) based on whether the year is a leap year. Other months have fixed lengths: April, June, September, and November have 30 days, while the rest have 31 days.

How to Create a Calendar Generator Using Java swing

Day of the Week Calculation

The getDayOfWeek method calculates the day of the week for the first day of the month using Zeller’s Congruence Algorithm in java , a mathematical algorithm. This method adjusts the month and year for January and February (treated as months 13 and 14 of the previous year) and computes the day of the week using modular arithmetic.

Calendar Generator Java Code

The getMonthCalendar method generates a formatted calendar for a given month and year. It uses the getDaysInMonth and getDayOfWeek methods to determine the layout of the calendar. The calendar is displayed in a grid format, with days of the week as headers. The current date is highlighted using square brackets [ ].

How to Create a Calendar Generator Using Java swing

2. Frontend GUI

The frontend is built using Java Swing, a GUI toolkit for Java. It provides a user-friendly interface for interacting with the calendar generator.

Main Window

The main window is a JFrame titled “✨ Cool Calendar Generator ✨”. It uses a gradient background for a modern look. The gradient is created using the GradientPaint class, which blends two colors (light sky blue and dodger blue) diagonally across the panel.

Calendar Display Area

The calendar is displayed in a JTextArea component, which is non-editable and uses a monospaced font (Consolas) for consistent alignment. The text area has a semi-transparent white background to ensure readability while maintaining the gradient effect.

Input Panel

The input panel contains:

  • Two text fields for entering the month and year.
  • Two buttons: View Month and View Year.

The input fields and buttons are styled with custom fonts, borders, and padding. The buttons also feature a hover effect that darkens their background color when the mouse pointer is over them.

Button Actions

  • View Month: When clicked, this button validates the input month and year, generates the calendar for the specified month, and displays it in the text area. If the input is invalid, an error message is shown.
  • View Year: This button generates and displays the calendar for all 12 months of the specified year.

Error Handling

The application includes error handling to ensure valid inputs. If the user enters an invalid month (e.g., 13) or non-numeric values, appropriate error messages are displayed in the calendar area.

NOTES

  • You can get its code from my GitHub repository
GitHub repository
  • Download the Zip File
Download Zip File

3. Key Features

Highlighting Today’s Date

The application uses the LocalDate class from the java.time package to get the current date. If the displayed calendar corresponds to the current month and year, the current date is highlighted using square brackets [ ].

Gradient Background

The gradient background is implemented by overriding the paintComponent method of the JPanel. This allows for custom rendering of the panel’s background.

Hover Effect on Buttons

The buttons have a hover effect that changes their background color when the mouse pointer is over them. This is achieved by adding a MouseListener to the buttons.

Scrollable Calendar Area

The calendar area is wrapped in a JScrollPane to ensure that the entire calendar is accessible, even if it exceeds the visible area of the window.

4. How the Application Works

  1. Launch the Application:
  • The main method initializes the GUI by invoking createAndShowGUI on the Event Dispatch Thread using SwingUtilities.invokeLater.
  1. User Interaction:
  • The user enters a month (1-12) and a year in the input fields.
  • Clicking View Month displays the calendar for the specified month.
  • Clicking View Year displays the calendar for all 12 months of the specified year.
  1. Calendar Generation:
  • The backend logic calculates the number of days in the month, the day of the week for the first day, and formats the calendar accordingly.
  • The current date is highlighted if applicable.
  1. Error Handling:
  • If the user enters invalid input (e.g., a month outside the range 1-12 or non-numeric values), an error message is displayed.

5. Extending the Application

This application can be extended with additional features, such as:

  • Exporting the Calendar: Save the generated calendar as a text file or PDF.
  • Adding Holidays: Highlight specific dates (e.g., public holidays) in the calendar.
  • Supporting Different Calendars: Implement support for lunar or other calendar systems.
  • Custom Themes: Allow users to choose different color schemes for the GUI.

Conclusion of Create a Calendar Generator Using Java Swing

The Calendar Generator is a practical and visually appealing application that demonstrates the power of Java Swing for building desktop GUIs. By combining backend logic for calendar generation with a modern and interactive frontend, this project provides a great learning opportunity for Java developers. Whether you’re a beginner or an experienced programmer, this project offers insights into date calculations, GUI design, and event handling in Java.

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Calendar Generator with Source Code in java with GUI

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

class CalendarGenerator {

    // Function to check if a year is a leap year
    public static boolean isLeapYear(int year) {
        return (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));
    }

    // Function to get the number of days in a month
    public static int getDaysInMonth(int month, int year) {
        switch (month) {
            case 2:
                return isLeapYear(year) ? 29 : 28;
            case 4: case 6: case 9: case 11:
                return 30;
            default:
                return 31;
        }
    }

    // Function to get the day of the week for the first day of the month
    public static int getDayOfWeek(int month, int year) {
        if (month < 3) {
            month += 12;
            year -= 1;
        }
        int k = year % 100;
        int j = year / 100;
        int day = 1 + (13 * (month + 1)) / 5 + k + (k / 4) + (j / 4) + 5 * j;
        return day % 7;
    }

    // Function to print a single month's calendar
    public static String getMonthCalendar(int month, int year) {
        String[] months = {"January", "February", "March", "April", "May", "June",
                "July", "August", "September", "October", "November", "December"};

        int daysInMonth = getDaysInMonth(month, year);
        int dayOfWeek = getDayOfWeek(month, year);

        StringBuilder calendar = new StringBuilder();
        calendar.append("\n-------------------------------------\n");
        calendar.append("           " + months[month - 1] + " " + year + "\n");
        calendar.append("-------------------------------------\n");
        calendar.append(" Sun  Mon  Tue  Wed  Thu  Fri  Sat\n");

        for (int i = 0; i < dayOfWeek; i++) {
            calendar.append("     ");
        }

        LocalDate today = LocalDate.now();
        for (int day = 1; day <= daysInMonth; day++) {
            if (year == today.getYear() && month == today.getMonthValue() && day == today.getDayOfMonth()) {
                calendar.append(String.format("[%2d] ", day)); // Highlight today's date
            } else {
                calendar.append(String.format("%4d ", day));
            }
            if ((day + dayOfWeek) % 7 == 0 || day == daysInMonth) {
                calendar.append("\n");
            }
        }

        return calendar.toString();
    }

    // GUI Implementation
    public static void createAndShowGUI() {
        JFrame frame = new JFrame("✨ Cool Calendar Generator ✨");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(800, 600);
        frame.setLayout(new BorderLayout());

        // Main Panel with Gradient Background
        JPanel mainPanel = new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                Graphics2D g2d = (Graphics2D) g;
                Color color1 = new Color(135, 206, 250); // Light Sky Blue
                Color color2 = new Color(30, 144, 255);  // Dodger Blue
                GradientPaint gradient = new GradientPaint(0, 0, color1, getWidth(), getHeight(), color2);
                g2d.setPaint(gradient);
                g2d.fillRect(0, 0, getWidth(), getHeight());
            }
        };
        mainPanel.setLayout(new BorderLayout());
        mainPanel.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));

        // Calendar Display Area
        JTextArea calendarArea = new JTextArea();
        calendarArea.setEditable(false);
        calendarArea.setFont(new Font("Consolas", Font.PLAIN, 16));
        calendarArea.setBackground(new Color(255, 255, 255, 150)); // Semi-transparent white
        calendarArea.setForeground(new Color(50, 50, 50));
        JScrollPane scrollPane = new JScrollPane(calendarArea);
        scrollPane.setBorder(BorderFactory.createLineBorder(new Color(200, 200, 200, 100), 1, true));
        scrollPane.setOpaque(false);
        scrollPane.getViewport().setOpaque(false);

        // Input Panel
        JPanel inputPanel = new JPanel();
        inputPanel.setLayout(new GridLayout(3, 2, 10, 10));
        inputPanel.setOpaque(false);

        JLabel monthLabel = new JLabel("Month (1-12):");
        monthLabel.setFont(new Font("Arial", Font.BOLD, 16));
        monthLabel.setForeground(Color.WHITE);
        JTextField monthField = new JTextField();
        monthField.setFont(new Font("Arial", Font.PLAIN, 16));
        monthField.setBorder(BorderFactory.createCompoundBorder(
                BorderFactory.createLineBorder(new Color(200, 200, 200), 1),
                BorderFactory.createEmptyBorder(5, 5, 5, 5)
        ));

        JLabel yearLabel = new JLabel("Year:");
        yearLabel.setFont(new Font("Arial", Font.BOLD, 16));
        yearLabel.setForeground(Color.WHITE);
        JTextField yearField = new JTextField();
        yearField.setFont(new Font("Arial", Font.PLAIN, 16));
        yearField.setBorder(BorderFactory.createCompoundBorder(
                BorderFactory.createLineBorder(new Color(200, 200, 200), 1),
                BorderFactory.createEmptyBorder(5, 5, 5, 5)
        ));

        JButton viewMonthButton = createStyledButton("View Month", new Color(0, 123, 255));
        JButton viewYearButton = createStyledButton("View Year", new Color(40, 167, 69));

        inputPanel.add(monthLabel);
        inputPanel.add(monthField);
        inputPanel.add(yearLabel);
        inputPanel.add(yearField);
        inputPanel.add(viewMonthButton);
        inputPanel.add(viewYearButton);

        // Add Components to Main Panel
        mainPanel.add(scrollPane, BorderLayout.CENTER);
        mainPanel.add(inputPanel, BorderLayout.SOUTH);

        // Button Actions
        viewMonthButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    int month = Integer.parseInt(monthField.getText());
                    int year = Integer.parseInt(yearField.getText());

                    if (month < 1 || month > 12) {
                        calendarArea.setText("Invalid month! Please enter a month between 1 and 12.");
                    } else {
                        calendarArea.setText(getMonthCalendar(month, year));
                    }
                } catch (NumberFormatException ex) {
                    calendarArea.setText("Please enter valid numeric values for month and year.");
                }
            }
        });

        viewYearButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    int year = Integer.parseInt(yearField.getText());
                    StringBuilder yearCalendar = new StringBuilder();

                    for (int month = 1; month <= 12; month++) {
                        yearCalendar.append(getMonthCalendar(month, year)).append("\n");
                    }

                    calendarArea.setText(yearCalendar.toString());
                } catch (NumberFormatException ex) {
                    calendarArea.setText("Please enter a valid numeric value for year.");
                }
            }
        });

        // Add Main Panel to Frame
        frame.add(mainPanel);
        frame.setVisible(true);
    }

    // Helper method to create styled buttons
    private static JButton createStyledButton(String text, Color color) {
        JButton button = new JButton(text);
        button.setFont(new Font("Arial", Font.BOLD, 16));
        button.setBackground(color);
        button.setForeground(Color.WHITE);
        button.setFocusPainted(false);
        button.setBorder(BorderFactory.createEmptyBorder(10, 20, 10, 20));
        button.setCursor(new Cursor(Cursor.HAND_CURSOR));

        // Hover Effect
        button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseEntered(java.awt.event.MouseEvent evt) {
                button.setBackground(color.darker());
            }

            public void mouseExited(java.awt.event.MouseEvent evt) {
                button.setBackground(color);
            }
        });

        return button;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGUI());
    }
}

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