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 javax.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ javax/sound/midi/spi/SoundbankReader.java

/*
 * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.sound.midi.spi;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import javax.sound.midi.InvalidMidiDataException;
import javax.sound.midi.Soundbank;

/**
 * A {@code SoundbankReader} supplies soundbank file-reading services. Concrete
 * subclasses of {@code SoundbankReader} parse a given soundbank file, producing
 * a {@link javax.sound.midi.Soundbank} object that can be loaded into a
 * {@link javax.sound.midi.Synthesizer}.
 *
 * @since 1.3
 * @author Kara Kytle
 */
public abstract class SoundbankReader {

    /**
     * Obtains a soundbank object from the URL provided.
     *
     * @param  url URL representing the soundbank.
     * @return soundbank object
     * @throws InvalidMidiDataException if the URL does not point to valid MIDI
     *         soundbank data recognized by this soundbank reader
     * @throws IOException if an I/O error occurs
     */
    public abstract Soundbank getSoundbank(URL url)
            throws InvalidMidiDataException, IOException;

    /**
     * Obtains a soundbank object from the {@code InputStream} provided.
     *
     * @param  stream {@code InputStream} representing the soundbank
     * @return soundbank object
     * @throws InvalidMidiDataException if the stream does not point to valid
     *         MIDI soundbank data recognized by this soundbank reader
     * @throws IOException if an I/O error occurs
     */
    public abstract Soundbank getSoundbank(InputStream stream)
            throws InvalidMidiDataException, IOException;

    /**
     * Obtains a soundbank object from the {@code File} provided.
     *
     * @param  file the {@code File} representing the soundbank
     * @return soundbank object
     * @throws InvalidMidiDataException if the file does not point to valid MIDI
     *         soundbank data recognized by this soundbank reader
     * @throws IOException if an I/O error occurs
     */
    public abstract Soundbank getSoundbank(File file)
            throws InvalidMidiDataException, IOException;
}

⏎ javax/sound/midi/spi/SoundbankReader.java

Or download all of them as a single archive file:

File name: jre-rt-javax-1.8.0_191-src.zip
File size: 5381005 bytes
Release date: 2018-10-28
Download 

⇒ JRE 8 rt.jar - org.* Package Source Code

⇐ JRE 8 rt.jar - java.* Package Source Code

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