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/mbeanserver/DescriptorCache.java

/*
 * Copyright (c) 2005, 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.mbeanserver;

import java.lang.ref.WeakReference;
import java.util.WeakHashMap;
import javax.management.Descriptor;
import javax.management.ImmutableDescriptor;
import javax.management.JMX;

public class DescriptorCache {
    private DescriptorCache() {
    }

    static DescriptorCache getInstance() {
        return instance;
    }

    public static DescriptorCache getInstance(JMX proof) {
        if (proof != null)
            return instance;
        else
            return null;
    }

    public ImmutableDescriptor get(ImmutableDescriptor descriptor) {
        WeakReference<ImmutableDescriptor> wr = map.get(descriptor);
        ImmutableDescriptor got = (wr == null) ? null : wr.get();
        if (got != null)
            return got;
        map.put(descriptor, new WeakReference<ImmutableDescriptor>(descriptor));
        return descriptor;
    }

    public ImmutableDescriptor union(Descriptor... descriptors) {
        return get(ImmutableDescriptor.union(descriptors));
    }

    private final static DescriptorCache instance = new DescriptorCache();
    private final WeakHashMap<ImmutableDescriptor,
                              WeakReference<ImmutableDescriptor>>
        map = new WeakHashMap<ImmutableDescriptor,
                              WeakReference<ImmutableDescriptor>>();
}

⏎ com/sun/jmx/mbeanserver/DescriptorCache.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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