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/pept/encoding/OutputObject.java

/*
 * Copyright (c) 2001, 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.corba.se.pept.encoding;

import java.io.IOException;

import com.sun.corba.se.pept.protocol.MessageMediator;

/**
 * <p> An <code>OutputObject</code> is the interface used by the
 * presentation block to give programming language typed data to
 * the encoding block to be encoded and sent in a message. </p>
 *
 * <p> The implementation of an <code>OutputObject</code> contains the
 * encoded data.  When the presentation block gives programming language
 * typed data to
 * <code>OutputObject</code>, the
 * implementation of <code>OutputObject</code> is responsible for converting
 * that data to the encoded representation of the data for a particular
 * encoding.</p>
 *
 * <p>A particular <em>encoding</em> would subclass
 * <code>OutputObject</code>.  The subclass would provide methods to set
 * the data types appropriate to the presentation block (e.g., simple
 * types such as int or boolean, all the way to any type derived from
 * <code>java.io.Serializable</code>.).</p>
 *
 * <p>Note: the protocol block may also use the <code>OutputObject</code> to
 * set header metadata.</p>
 *
 * @author Harold Carr
*/
public interface OutputObject
{
    public void setMessageMediator(MessageMediator messageMediator);

    public MessageMediator getMessageMediator();

    public void close() throws IOException;
}

// End of file.

⏎ com/sun/corba/se/pept/encoding/OutputObject.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)