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/impl/protocol/giopmsgheaders/CancelRequestMessage_1_2.java

/*
 * Copyright (c) 2000, 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
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 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.corba.se.impl.protocol.giopmsgheaders;

import com.sun.corba.se.spi.ior.iiop.GIOPVersion;

/**
 * This implements the GIOP 1.2 CancelRequest header.
 *
 * @author Ram Jeyaraman 05/14/2000
 */

public final class CancelRequestMessage_1_2 extends Message_1_1
        implements CancelRequestMessage {

    // Instance variables

    private int request_id = (int) 0;

    // Constructors

    CancelRequestMessage_1_2() {}

    CancelRequestMessage_1_2(int _request_id) {
        super(Message.GIOPBigMagic, GIOPVersion.V1_2, FLAG_NO_FRAG_BIG_ENDIAN,
            Message.GIOPCancelRequest, CANCEL_REQ_MSG_SIZE);
        request_id = _request_id;
    }

    // Accessor methods

    public int getRequestId() {
        return this.request_id;
    }

    // IO methods

    public void read(org.omg.CORBA.portable.InputStream istream) {
        super.read(istream);
        this.request_id = istream.read_ulong();
    }

    public void write(org.omg.CORBA.portable.OutputStream ostream) {
        super.write(ostream);
        ostream.write_ulong(this.request_id);
    }

    public void callback(MessageHandler handler)
        throws java.io.IOException
    {
        handler.handleInput(this);
    }
} // class CancelRequestMessage_1_2

⏎ com/sun/corba/se/impl/protocol/giopmsgheaders/CancelRequestMessage_1_2.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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