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/monitoring/MonitoredAttributeInfo.java

/*
 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */
package com.sun.corba.se.spi.monitoring;

import java.util.*;

/**
 * <p>
 *
 * @author Hemanth Puttaswamy
 * </p>
 * <p>
 * Monitored AttributeInfo contains the meta information of the Monitored
 * Attribute.
 * </p>
 */
public interface MonitoredAttributeInfo {

  ///////////////////////////////////////
  // operations

/**
 * <p>
 * If the Attribute is writable from ASAdmin then isWritable() will return
 * true.
 * </p>
 * <p>
 *
 * @return a boolean with true or false
 * </p>
 */
    public boolean isWritable();
/**
 * <p>
 * isStatistic() is true if the attribute is presented as a Statistic.
 * </p>
 * <p>
 *
 * @return a boolean with true or false
 * </p>
 */
    public boolean isStatistic();
/**
 * <p>
 * Class Type: We will allow only basic class types: 1)Boolean 2)Integer
 * 3)Byte 4)Long 5)Float 6)Double 7)String 8)Character
 * </p>
 * <p>
 *
 * @return a Class Type
 * </p>
 */
    public Class type();
/**
 * <p>
 * Get's the description for the Monitored Attribute.
 * </p>
 * <p>
 *
 * @return a String with description
 * </p>
 */
    public String getDescription();

} // end MonitoredAttributeInfo

⏎ com/sun/corba/se/spi/monitoring/MonitoredAttributeInfo.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)