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/internal/ProxyRef.java

/*
 * Copyright (c) 2003, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
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 */

package com.sun.jmx.remote.internal;

import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.lang.reflect.Method;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.server.RemoteObject;
import java.rmi.server.RemoteRef;


@SuppressWarnings("deprecation")
public class ProxyRef implements RemoteRef {
    private static final long serialVersionUID = -6503061366316814723L;

    public ProxyRef(RemoteRef ref) {
        this.ref = ref;
    }

    public void readExternal(ObjectInput in)
            throws IOException, ClassNotFoundException {
        ref.readExternal(in);
    }

    public void writeExternal(ObjectOutput out) throws IOException {
        ref.writeExternal(out);
    }

    /**
     * @deprecated
     */
    @Deprecated
    public void invoke(java.rmi.server.RemoteCall call) throws Exception {
        ref.invoke(call);
    }

    public Object invoke(Remote obj, Method method, Object[] params,
                         long opnum) throws Exception {
        return ref.invoke(obj, method, params, opnum);
    }

    /**
     * @deprecated
     */
    @Deprecated
    public void done(java.rmi.server.RemoteCall call) throws RemoteException {
        ref.done(call);
    }

    public String getRefClass(ObjectOutput out) {
        return ref.getRefClass(out);
    }

    /**
     * @deprecated
     */
    @Deprecated
    public java.rmi.server.RemoteCall newCall(RemoteObject obj,
            java.rmi.server.Operation[] op, int opnum,
                              long hash) throws RemoteException {
        return ref.newCall(obj, op, opnum, hash);
    }

    public boolean remoteEquals(RemoteRef obj) {
        return ref.remoteEquals(obj);
    }

    public int remoteHashCode() {
        return ref.remoteHashCode();
    }

    public String remoteToString() {
        return ref.remoteToString();
    }

    protected RemoteRef ref;
}

⏎ com/sun/jmx/remote/internal/ProxyRef.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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