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General Rules for Using Swing Components

This section has general information on what Swing components have in common. It tells you about features that the JComponent class provides to most Swing components, including code on how to use these features.

What the JComponent Class Provides

Most Swing components are implemented as subclasses of the JComponent(in the API reference documentation) class, which inherits from the Component class. From JComponent, Swing components inherit the following functionality:
Borders.
Using the setBorder method, you can specify the border that a component displays around its edges. You can specify that a component have extra space around its edges using an EmptyBorder instance. See [x-ref].

Double buffering.
Double buffering can improve the appearance of a frequently changing component. Now you don't have to write the double buffering code -- Swing provides it for you. By invoking setDoubleBuffered(true) on a component, you make it double buffered.

Tool tips.
By specifying a string with the setToolTip method, you can provide help to users of a component. When the cursor pauses over the component, the specified string is displayed in a small window that appears near the component. See How to Use Tool Tips for more information.

Keyboard-generated actions.
Using the registerKeyboardAction method, you can enable the user to use the keyboard, instead of the mouse, to indicate that the component's action should occur.
Note: Some classes provide convenience methods for keyboard actions. For example, AbstractButton provides setKeyAccelerator, which lets you specify the character that, in combination with a look-and-feel-specific modifier key, causes the button's action to be performed. See How to Use Buttons for an example of using key accelerators in buttons.
The combination of character and modifier keys that the user must press to start an action is represented by a JKeyStroke object. The resulting action event is handled by a JAction object. Each keyboard action works under exactly one of two conditions: either when the actual component has the focus or when any component in its containing window has the focus.

Support for scrolling.
With the computeVisibleRect and getVisibleRect methods, you can determine what part of a component might be visible onscreen. This is especially handy for improving the performance of scrolling. [CHECK] The scrollRectToVisible method sends a message to the JComponent's parent, requesting that it display the specified area. With the setAutoscrolls method, you can specify that a component should automatically scroll when dragged, if its container is one (such as JViewport) that supports scrolling.

Properties.
With the putProperty method, you can associate one or more properties (name/object pairs) with any JComponent. For example, a layout manager might use properties to associate a constraints object with each JComponent it manages. You get properties using the getProperty method.

Application-wide pluggable look and feel.
Each Java runtime has a UIFactory object that determines the look and feel of that runtime's Swing components. Subject to security restrictions, you can choose the look and feel used by all Swing components by invoking the UIManager.setUIFactory method. Behind the scenes, each JComponent object has a corresponding ComponentUI object (created by the UIFactory) that performs all the drawing, event handling, size determination, and so on for that JComponent.

Note: If you want to change the look and feel of an individual Swing component, rather than the whole set of Swing components, you should reimplement the individual component [point to doc]. To learn about implementing a look-and-feel package, [wait for doc!].

Support for layout.
With methods such as setPreferredSize, setMinimumSize, setMaximumSize, setAlignmentX, and setAlignmentY, you can specify layout constraints without having to write your own component.

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