Swing

Swing is not your only choice for GUI development, but it is available to you "out of the box." The Eclipse IDE was built using SWT (Standard Widget Toolkit), an API that you could also choose to use for your applications.

Swing is actually built atop another Java API known as AWT (Abstract Window Toolkit). Sun introduced AWT with the first version of Java as the sole means for producing GUIs. It consisted of a small number of widgets that at the time were guaranteed to be available on all platforms supported by Java. This "lowest common denominator" design decision allowed you to build cross-platform GUI applications but restricted your expressiveness with respect to GUI design.

AWT is known as a heavyweight GUI framework. Java tightly couples each AWT control to an equivalent control directly supported by the operating system. The operating system manages each AWT control.

Swing, which was introduced a few years after AWT, is, in contrast, a lightweight GUI framework. Swing eliminates the lowest common denominator problem by creating controls that use heavyweight controls as a "shell." Swing components inherit from AWT components. They add custom rendering and interaction code so that they act and look far more sophisticated than the controls supported by all operating systems.

You can attach a look and feel to your Swing application so that it mimics a specific operating system. For example, you can tell Java to render your Swing controls so that they look like Motif controls or like Windows controls.