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/naming/cosnaming/NamingUtils.java

/*
 * Copyright (c) 1997, 2003, 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.corba.se.impl.naming.cosnaming;

import java.io.*;
import org.omg.CosNaming.NameComponent;


public class NamingUtils {
    // Do not instantiate this class
    private NamingUtils() {};

    /**
     * Debug flag which must be true for debug streams to be created and
     * dprint output to be generated.
     */
    public static boolean debug = false;

    /**
     * Prints the message to the debug stream if debugging is enabled.
     * @param msg the debug message to print.
     */
    public static void dprint(String msg) {
        if (debug && debugStream != null)
            debugStream.println(msg);
    }

    /**
     * Prints the message to the error stream (System.err is default).
     * @param msg the error message to print.
     */
    public static void errprint(String msg) {
        if (errStream != null)
            errStream.println(msg);
        else
            System.err.println(msg);
    }

    /**
     * Prints the stacktrace of the supplied exception to the error stream.
     * @param e any Java exception.
     */
    public static void printException(java.lang.Exception e) {
        if (errStream != null)
            e.printStackTrace(errStream);
        else
            e.printStackTrace();
    }

    /**
     * Create a debug print stream to the supplied log file.
     * @param logFile the file to which debug output will go.
     * @exception IOException thrown if the file cannot be opened for output.
     */
    public static void makeDebugStream(File logFile)
        throws java.io.IOException {
        // Create an outputstream for debugging
        java.io.OutputStream logOStream =
            new java.io.FileOutputStream(logFile);
        java.io.DataOutputStream logDStream =
            new java.io.DataOutputStream(logOStream);
        debugStream = new java.io.PrintStream(logDStream);

        // Emit first message
        debugStream.println("Debug Stream Enabled.");
    }

    /**
     * Create a error print stream to the supplied file.
     * @param logFile the file to which error messages will go.
     * @exception IOException thrown if the file cannot be opened for output.
     */
    public static void makeErrStream(File errFile)
        throws java.io.IOException {
        if (debug) {
            // Create an outputstream for errors
            java.io.OutputStream errOStream =
                new java.io.FileOutputStream(errFile);
            java.io.DataOutputStream errDStream =
                new java.io.DataOutputStream(errOStream);
            errStream = new java.io.PrintStream(errDStream);
            dprint("Error stream setup completed.");
        }
    }


    /**
     * A utility method that takes Array of NameComponent and converts
     * into a directory structured name in the format of /id1.kind1/id2.kind2..
     * This is used mainly for Logging.
     */
    static String getDirectoryStructuredName( NameComponent[] name ) {
        StringBuffer directoryStructuredName = new StringBuffer("/");
        for( int i = 0; i < name.length; i++ ) {
            directoryStructuredName.append( name[i].id + "." + name[i].kind );
        }
        return directoryStructuredName.toString( );
    }

    /**
     * The debug printstream.
     */
    public static java.io.PrintStream debugStream;

    /**
     * The error printstream.
     */
    public static java.io.PrintStream errStream;
}

⏎ com/sun/corba/se/impl/naming/cosnaming/NamingUtils.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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