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

⏎ java/awt/peer/TrayIconPeer.java

/*
 * Copyright (c) 2005, 2007, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.awt.peer;

import java.awt.SystemTray;
import java.awt.TrayIcon;

/**
 * The peer interface for the {@link TrayIcon}. This doesn't need to be
 * implemented if {@link SystemTray#isSupported()} returns false.
 */
public interface TrayIconPeer {

    /**
     * Disposes the tray icon and releases and resources held by it.
     *
     * @see TrayIcon#removeNotify()
     */
    void dispose();

    /**
     * Sets the tool tip for the tray icon.
     *
     * @param tooltip the tooltip to set
     *
     * @see TrayIcon#setToolTip(String)
     */
    void setToolTip(String tooltip);

    /**
     * Updates the icon image. This is supposed to display the current icon
     * from the TrayIcon component in the actual tray icon.
     *
     * @see TrayIcon#setImage(java.awt.Image)
     * @see TrayIcon#setImageAutoSize(boolean)
     */
    void updateImage();

    /**
     * Displays a message at the tray icon.
     *
     * @param caption the message caption
     * @param text the actual message text
     * @param messageType the message type
     *
     * @see TrayIcon#displayMessage(String, String, java.awt.TrayIcon.MessageType)
     */
    void displayMessage(String caption, String text, String messageType);

    /**
     * Shows the popup menu of this tray icon at the specified position.
     *
     * @param x the X location for the popup menu
     * @param y the Y location for the popup menu
     */
    void showPopupMenu(int x, int y);
}

⏎ java/awt/peer/TrayIconPeer.java

Or download all of them as a single archive file:

File name: jre-rt-java-1.8.0_191-src.zip
File size: 6664831 bytes
Release date: 2018-10-28
Download 

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