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 org.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ org/xml/sax/SAXNotSupportedException.java

/*
 * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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// SAXNotSupportedException.java - unsupported feature or value.
// http://www.saxproject.org
// Written by David Megginson
// NO WARRANTY!  This class is in the Public Domain.
// $Id: SAXNotSupportedException.java,v 1.4 2004/11/03 22:55:32 jsuttor Exp $

package org.xml.sax;

/**
 * Exception class for an unsupported operation.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
 * for further information.
 * </blockquote>
 *
 * <p>An XMLReader will throw this exception when it recognizes a
 * feature or property identifier, but cannot perform the requested
 * operation (setting a state or value).  Other SAX2 applications and
 * extensions may use this class for similar purposes.</p>
 *
 * @since SAX 2.0
 * @author David Megginson
 * @see org.xml.sax.SAXNotRecognizedException
 */
public class SAXNotSupportedException extends SAXException
{

    /**
     * Construct a new exception with no message.
     */
    public SAXNotSupportedException ()
    {
        super();
    }


    /**
     * Construct a new exception with the given message.
     *
     * @param message The text message of the exception.
     */
    public SAXNotSupportedException (String message)
    {
        super(message);
    }

    // Added serialVersionUID to preserve binary compatibility
    static final long serialVersionUID = -1422818934641823846L;
}

// end of SAXNotSupportedException.java

⏎ org/xml/sax/SAXNotSupportedException.java

Or download all of them as a single archive file:

File name: jre-rt-org-1.8.0_191-src.zip
File size: 951125 bytes
Release date: 2018-10-28
Download 

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

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

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⇑⇑ FAQ for JDK (Java Development Kit)