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 com.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ com/sun/corba/se/PortableActivationIDL/_ServerProxyImplBase.java

package com.sun.corba.se.PortableActivationIDL;


/**
* com/sun/corba/se/PortableActivationIDL/_ServerProxyImplBase.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/com/sun/corba/se/PortableActivationIDL/activation.idl
* Saturday, October 6, 2018 9:30:40 AM PDT
*/


/** Server callback interface, passed to Activator in registerServer method.
    */
public abstract class _ServerProxyImplBase extends org.omg.CORBA.portable.ObjectImpl
                implements com.sun.corba.se.PortableActivationIDL.ServerProxy, org.omg.CORBA.portable.InvokeHandler
{

  // Constructors
  public _ServerProxyImplBase ()
  {
  }

  private static java.util.Hashtable _methods = new java.util.Hashtable ();
  static
  {
    _methods.put ("shutdown", new java.lang.Integer (0));
    _methods.put ("install", new java.lang.Integer (1));
    _methods.put ("uninstall", new java.lang.Integer (2));
  }

  public org.omg.CORBA.portable.OutputStream _invoke (String $method,
                                org.omg.CORBA.portable.InputStream in,
                                org.omg.CORBA.portable.ResponseHandler $rh)
  {
    org.omg.CORBA.portable.OutputStream out = null;
    java.lang.Integer __method = (java.lang.Integer)_methods.get ($method);
    if (__method == null)
      throw new org.omg.CORBA.BAD_OPERATION (0, org.omg.CORBA.CompletionStatus.COMPLETED_MAYBE);

    switch (__method.intValue ())
    {

  /** Shutdown this server.  Returns after orb.shutdown() completes.
	*/
       case 0:  // PortableActivationIDL/ServerProxy/shutdown
       {
         this.shutdown ();
         out = $rh.createReply();
         break;
       }


  /** Install the server.  Returns after the install hook completes
	* execution in the server.
	*/
       case 1:  // PortableActivationIDL/ServerProxy/install
       {
         this.install ();
         out = $rh.createReply();
         break;
       }


  /** Uninstall the server.  Returns after the uninstall hook
	* completes execution.
	*/
       case 2:  // PortableActivationIDL/ServerProxy/uninstall
       {
         this.uninstall ();
         out = $rh.createReply();
         break;
       }

       default:
         throw new org.omg.CORBA.BAD_OPERATION (0, org.omg.CORBA.CompletionStatus.COMPLETED_MAYBE);
    }

    return out;
  } // _invoke

  // Type-specific CORBA::Object operations
  private static String[] __ids = {
    "IDL:PortableActivationIDL/ServerProxy:1.0"};

  public String[] _ids ()
  {
    return (String[])__ids.clone ();
  }


} // class _ServerProxyImplBase

⏎ com/sun/corba/se/PortableActivationIDL/_ServerProxyImplBase.java

Or download all of them as a single archive file:

File name: jre-rt-com-1.8.0_191-src.zip
File size: 8099783 bytes
Release date: 2018-10-28
Download 

⇒ Backup JDK 8 Installation Directory

⇐ JRE 8 rt.jar - org.* Package Source Code

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)