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/html/HTMLAppletElement.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.html;

/**
 *  An embedded Java applet. See the  APPLET element definition in HTML 4.0.
 * This element is deprecated in HTML 4.0.
 * <p>See also the <a href='http://www.w3.org/TR/2000/CR-DOM-Level-2-20000510'>Document Object Model (DOM) Level 2 Specification</a>.
 */
public interface HTMLAppletElement extends HTMLElement {
    /**
     *  Aligns this object (vertically or horizontally)  with respect to its
     * surrounding text. See the  align attribute definition in HTML 4.0.
     * This attribute is deprecated in HTML 4.0.
     */
    public String getAlign();
    public void setAlign(String align);

    /**
     *  Alternate text for user agents not rendering the normal content of
     * this element. See the  alt attribute definition in HTML 4.0. This
     * attribute is deprecated in HTML 4.0.
     */
    public String getAlt();
    public void setAlt(String alt);

    /**
     *  Comma-separated archive list. See the  archive attribute definition in
     * HTML 4.0. This attribute is deprecated in HTML 4.0.
     */
    public String getArchive();
    public void setArchive(String archive);

    /**
     *  Applet class file.  See the  code attribute definition in HTML 4.0.
     * This attribute is deprecated in HTML 4.0.
     */
    public String getCode();
    public void setCode(String code);

    /**
     *  Optional base URI for applet. See the  codebase attribute definition
     * in HTML 4.0. This attribute is deprecated in HTML 4.0.
     */
    public String getCodeBase();
    public void setCodeBase(String codeBase);

    /**
     *  Override height. See the  height attribute definition in HTML 4.0.
     * This attribute is deprecated in HTML 4.0.
     */
    public String getHeight();
    public void setHeight(String height);

    /**
     *  Horizontal space to the left and right of this image, applet, or
     * object. See the  hspace attribute definition in HTML 4.0. This
     * attribute is deprecated in HTML 4.0.
     */
    public String getHspace();
    public void setHspace(String hspace);

    /**
     *  The name of the applet. See the  name attribute definition in HTML
     * 4.0. This attribute is deprecated in HTML 4.0.
     */
    public String getName();
    public void setName(String name);

    /**
     *  Serialized applet file. See the  object attribute definition in HTML
     * 4.0. This attribute is deprecated in HTML 4.0.
     */
    public String getObject();
    public void setObject(String object);

    /**
     *  Vertical space above and below this image, applet, or object. See the
     * vspace attribute definition in HTML 4.0. This attribute is deprecated
     * in HTML 4.0.
     */
    public String getVspace();
    public void setVspace(String vspace);

    /**
     *  Override width. See the  width attribute definition in HTML 4.0. This
     * attribute is deprecated in HTML 4.0.
     */
    public String getWidth();
    public void setWidth(String width);

}

⏎ org/w3c/dom/html/HTMLAppletElement.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

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)