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/spi/activation/ServerIdsHolder.java

package com.sun.corba.se.spi.activation;


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

public final class ServerIdsHolder implements org.omg.CORBA.portable.Streamable
{
  public int value[] = null;

  public ServerIdsHolder ()
  {
  }

  public ServerIdsHolder (int[] initialValue)
  {
    value = initialValue;
  }

  public void _read (org.omg.CORBA.portable.InputStream i)
  {
    value = com.sun.corba.se.spi.activation.ServerIdsHelper.read (i);
  }

  public void _write (org.omg.CORBA.portable.OutputStream o)
  {
    com.sun.corba.se.spi.activation.ServerIdsHelper.write (o, value);
  }

  public org.omg.CORBA.TypeCode _type ()
  {
    return com.sun.corba.se.spi.activation.ServerIdsHelper.type ();
  }

}

⏎ com/sun/corba/se/spi/activation/ServerIdsHolder.java

⇒ Backup JDK 8 Installation Directory

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

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)