This Java program demonstrates the use of radio buttons (JRadioButton) and button groups (ButtonGroup) in a graphical user interface (GUI) using Swing.
The program allows the user to select different font styles (Plain, Bold, Italic, and Bold/Italic) for a text field (JTextField).
When the user clicks a radio button, the text field's font changes accordingly.
Four font style options: Plain, Bold, Italic, and Bold/Italic.
Updates the text field in real-time based on the selected radio button.
Uses Swing components for GUI elements.