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/w3c/dom/css/CSSPageRule.java

/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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/*
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 * Copyright (c) 2000 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program 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 W3C License http://www.w3.org/Consortium/Legal/ for more details.
 */

package org.w3c.dom.css;

import org.w3c.dom.DOMException;

/**
 *  The <code>CSSPageRule</code> interface represents a @page rule within a
 * CSS style sheet. The <code>@page</code> rule is used to specify the
 * dimensions, orientation, margins, etc. of a page box for paged media.
 * <p>See also the <a href='http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113'>Document Object Model (DOM) Level 2 Style Specification</a>.
 * @since DOM Level 2
 */
public interface CSSPageRule extends CSSRule {
    /**
     *  The parsable textual representation of the page selector for the rule.
     */
    public String getSelectorText();
    /**
     *  The parsable textual representation of the page selector for the rule.
     * @exception DOMException
     *   SYNTAX_ERR: Raised if the specified CSS string value has a syntax
     *   error and is unparsable.
     *   <br>NO_MODIFICATION_ALLOWED_ERR: Raised if this rule is readonly.
     */
    public void setSelectorText(String selectorText)
                           throws DOMException;

    /**
     *  The declaration-block of this rule.
     */
    public CSSStyleDeclaration getStyle();

}

⏎ org/w3c/dom/css/CSSPageRule.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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