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/HTMLIFrameElement.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;

import org.w3c.dom.Document;

/**
 *  Inline subwindows. See the  IFRAME element definition 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 HTMLIFrameElement 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);

    /**
     *  Request frame borders. See the  frameborder attribute definition in
     * HTML 4.0.
     */
    public String getFrameBorder();
    public void setFrameBorder(String frameBorder);

    /**
     *  Frame height. See the  height attribute definition in HTML 4.0.
     */
    public String getHeight();
    public void setHeight(String height);

    /**
     *  URI designating a long description of this image or frame. See the
     * longdesc attribute definition in HTML 4.0.
     */
    public String getLongDesc();
    public void setLongDesc(String longDesc);

    /**
     *  Frame margin height, in pixels. See the  marginheight attribute
     * definition in HTML 4.0.
     */
    public String getMarginHeight();
    public void setMarginHeight(String marginHeight);

    /**
     *  Frame margin width, in pixels. See the  marginwidth attribute
     * definition in HTML 4.0.
     */
    public String getMarginWidth();
    public void setMarginWidth(String marginWidth);

    /**
     *  The frame name (object of the <code>target</code> attribute). See the
     * name attribute definition in HTML 4.0.
     */
    public String getName();
    public void setName(String name);

    /**
     *  Specify whether or not the frame should have scrollbars. See the
     * scrolling attribute definition in HTML 4.0.
     */
    public String getScrolling();
    public void setScrolling(String scrolling);

    /**
     *  A URI designating the initial frame contents. See the  src attribute
     * definition in HTML 4.0.
     */
    public String getSrc();
    public void setSrc(String src);

    /**
     *  Frame width. See the  width attribute definition in HTML 4.0.
     */
    public String getWidth();
    public void setWidth(String width);

    /**
     *  The document this frame contains, if there is any and it is available,
     * or <code>null</code> otherwise.
     * @since DOM Level 2
     */
    public Document getContentDocument();

}

⏎ org/w3c/dom/html/HTMLIFrameElement.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)