https://openjdk.java.net/ 
/*
 * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */


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.

Since:1.2
@serialexclude
/**
 * 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 {@code javax.swing.plaf.basic} and
 * {@code javax.swing.plaf.metal} packages).
 * <p>
 * <strong>Note:</strong>
 * Most of the Swing API is <em>not</em> thread safe. For details, see
 * <a
 * href="https://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html"
 * target="_top">Concurrency in Swing</a>,
 * a section in
 * <em><a href="https://docs.oracle.com/javase/tutorial/"
 * target="_top">The Java Tutorial</a></em>.
 *
 * @since 1.2
 * @serial exclude
 */
package javax.swing.plaf;