Provides one interface and many abstract classes that Swing uses to provide
its pluggable look-and-feel capabilities. Its classes are subclassed and
implemented by look and feel UIs such as Basic and the Java look and feel
(Metal). This package is only used by developers who cannot create a new
look and feel by subclassing existing look-and-feel components (such as those
provided by the javax.swing.plaf.basic and
javax.swing.plaf.metal packages).
Note: Most of the Swing API is not thread safe. For details, see Concurrency in Swing, a section in The Java Tutorial.