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/DOMStringList.java

/*
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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/*
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 * Copyright (c) 2004 World Wide Web Consortium,
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 * (Massachusetts Institute of Technology, European Research Consortium for
 * Informatics and Mathematics, Keio University). All Rights Reserved. This
 * work is distributed under the W3C(r) Software License [1] 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.
 *
 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
 */

package org.w3c.dom;

/**
 *  The <code>DOMStringList</code> interface provides the abstraction of an
 * ordered collection of <code>DOMString</code> values, without defining or
 * constraining how this collection is implemented. The items in the
 * <code>DOMStringList</code> are accessible via an integral index, starting
 * from 0.
 * <p>See also the <a href='http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407'>Document Object Model (DOM) Level 3 Core Specification</a>.
 * @since DOM Level 3
 */
public interface DOMStringList {
    /**
     *  Returns the <code>index</code>th item in the collection. If
     * <code>index</code> is greater than or equal to the number of
     * <code>DOMString</code>s in the list, this returns <code>null</code>.
     * @param index Index into the collection.
     * @return  The <code>DOMString</code> at the <code>index</code>th
     *   position in the <code>DOMStringList</code>, or <code>null</code> if
     *   that is not a valid index.
     */
    public String item(int index);

    /**
     * The number of <code>DOMString</code>s in the list. The range of valid
     * child node indices is 0 to <code>length-1</code> inclusive.
     */
    public int getLength();

    /**
     *  Test if a string is part of this <code>DOMStringList</code>.
     * @param str  The string to look for.
     * @return  <code>true</code> if the string has been found,
     *   <code>false</code> otherwise.
     */
    public boolean contains(String str);

}

⏎ org/w3c/dom/DOMStringList.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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