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/jmx/remote/protocol/rmi/ServerProvider.java

/*
 * Copyright (c) 2003, 2004, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package com.sun.jmx.remote.protocol.rmi;

import java.io.IOException;
import java.net.MalformedURLException;
import java.util.Map;

import javax.management.MBeanServer;
import javax.management.remote.JMXConnectorServer;
import javax.management.remote.JMXConnectorServerProvider;
import javax.management.remote.JMXServiceURL;
import javax.management.remote.rmi.RMIConnectorServer;

public class ServerProvider implements JMXConnectorServerProvider {

    public JMXConnectorServer newJMXConnectorServer(JMXServiceURL serviceURL,
                                                    Map<String,?> environment,
                                                    MBeanServer mbeanServer)
            throws IOException {
        if (!serviceURL.getProtocol().equals("rmi")) {
            throw new MalformedURLException("Protocol not rmi: " +
                                            serviceURL.getProtocol());
        }
        return new RMIConnectorServer(serviceURL, environment, mbeanServer);
    }

}

⏎ com/sun/jmx/remote/protocol/rmi/ServerProvider.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 

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