JFrames

JFrame is a top-level window provided by the Swing library for Java applications. It represents a window on the screen with a title bar, borders, and standard window controls, and it serves as the main container for a Swing-based user interface. A JFrame is a subclass of java.awt.Frame and, as a Swing top-level container, contains a root pane that coordinates a layered pane, a content pane, and a glass pane.

Components are typically added to the frame’s content pane. Although modern code can call add(component) directly on the frame, the traditional approach is frame.getContentPane().add(component) and to set a layout on that pane.

Common operations include setting the title (setTitle), size or preferred size (setSize, pack), resizability (setResizable), and the default close behavior (setDefaultCloseOperation). To show the window, make it visible (setVisible(true)); centering on screen is often done with setLocationRelativeTo(null). When the user closes the frame, the operating system or program will dispose of resources depending on the chosen close operation, such as EXIT_ON_CLOSE or DISPOSE_ON_CLOSE.

Frames should be created and updated on the Event Dispatch Thread, as Swing is not fully thread-safe. Typical practice uses SwingUtilities.invokeLater to construct and display the GUI from the main method.

JFrame is commonly used as the main window, while auxiliary windows are created with JDialog or JWindow. The frame’s content pane holds the actual UI components, arranged with a chosen layout manager.