JRE 8 rt.jar is the JAR file for JRE 8 RT (Runtime) libraries. JRE (Java Runtime) 8 is the runtime environment included in JDK 8. JRE 8 rt.jar libraries are divided into 6 packages:

com.* - Internal Oracle and Sun Microsystems libraries
java.* - Standard Java API libraries.
javax.* - Extended Java API libraries.
jdk.* -  JDK supporting libraries.
org.* - Third party libraries.
sun.* - Old libraries developed by Sun Microsystems.

JAR File Information:

Directory of C:\fyicenter\jdk-1.8.0_191\jre\lib
      63,596,151 rt.jar

Here is the list of Java classes of the javax.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ javax/swing/InternalFrameFocusTraversalPolicy.java

/*
 * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package javax.swing;


import java.awt.Component;
import java.awt.FocusTraversalPolicy;

/**
 * A FocusTraversalPolicy which can optionally provide an algorithm for
 * determining a JInternalFrame's initial Component. The initial Component is
 * the first to receive focus when the JInternalFrame is first selected. By
 * default, this is the same as the JInternalFrame's default Component to
 * focus.
 *
 * @author David Mendenhall
 *
 * @since 1.4
 */
public abstract class InternalFrameFocusTraversalPolicy
    extends FocusTraversalPolicy
{

    /**
     * Returns the Component that should receive the focus when a
     * JInternalFrame is selected for the first time. Once the JInternalFrame
     * has been selected by a call to <code>setSelected(true)</code>, the
     * initial Component will not be used again. Instead, if the JInternalFrame
     * loses and subsequently regains selection, or is made invisible or
     * undisplayable and subsequently made visible and displayable, the
     * JInternalFrame's most recently focused Component will become the focus
     * owner. The default implementation of this method returns the
     * JInternalFrame's default Component to focus.
     *
     * @param frame the JInternalFrame whose initial Component is to be
     *        returned
     * @return the Component that should receive the focus when frame is
     *         selected for the first time, or null if no suitable Component
     *         can be found
     * @see JInternalFrame#getMostRecentFocusOwner
     * @throws IllegalArgumentException if window is null
     */
    public Component getInitialComponent(JInternalFrame frame) {
        return getDefaultComponent(frame);
    }
}

⏎ javax/swing/InternalFrameFocusTraversalPolicy.java

Or download all of them as a single archive file:

File name: jre-rt-javax-1.8.0_191-src.zip
File size: 5381005 bytes
Release date: 2018-10-28
Download 

⇒ JRE 8 rt.jar - org.* Package Source Code

⇐ JRE 8 rt.jar - java.* Package Source Code

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