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/omg/PortableInterceptor/InterceptorOperations.java

package org.omg.PortableInterceptor;


/**
* org/omg/PortableInterceptor/InterceptorOperations.java .
* Generated by the IDL-to-Java compiler (portable), version "3.2"
* from c:/re/workspace/8-2-build-windows-amd64-cygwin/jdk8u191/11896/corba/src/share/classes/org/omg/PortableInterceptor/Interceptors.idl
* Saturday, October 6, 2018 9:30:42 AM PDT
*/


/**
   * All Portable Interceptors implement Interceptor.
   */
public interface InterceptorOperations 
{

  /**
     * Returns the name of the interceptor.
     * <p>
     * Each Interceptor may have a name that may be used administratively 
     * to order the lists of Interceptors. Only one Interceptor of a given 
     * name can be registered with the ORB for each Interceptor type. An 
     * Interceptor may be anonymous, i.e., have an empty string as the name 
     * attribute. Any number of anonymous Interceptors may be registered with 
     * the ORB.
     *
     * @return the name of the interceptor.
     */
  String name ();

  /**
     * Provides an opportunity to destroy this interceptor.
     * The destroy method is called during <code>ORB.destroy</code>. When an 
     * application calls <code>ORB.destroy</code>, the ORB:
     * <ol>
     *   <li>waits for all requests in progress to complete</li>
     *   <li>calls the <code>Interceptor.destroy</code> operation for each 
     *       interceptor</li>
     *   <li>completes destruction of the ORB</li>
     * </ol>
     * Method invocations from within <code>Interceptor.destroy</code> on 
     * object references for objects implemented on the ORB being destroyed 
     * result in undefined behavior. However, method invocations on objects 
     * implemented on an ORB other than the one being destroyed are 
     * permitted. (This means that the ORB being destroyed is still capable 
     * of acting as a client, but not as a server.) 
     */
  void destroy ();
} // interface InterceptorOperations

⏎ org/omg/PortableInterceptor/InterceptorOperations.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)