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/management/timer/TimerAlarmClock.java

/*
 * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package javax.management.timer;

import java.util.Date;
import java.util.logging.Level;
import static com.sun.jmx.defaults.JmxProperties.TIMER_LOGGER;

/**
 * This class provides a simple implementation of an alarm clock MBean.
 * The aim of this MBean is to set up an alarm which wakes up the timer every timeout (fixed-delay)
 * or at the specified date (fixed-rate).
 */

class TimerAlarmClock extends java.util.TimerTask {

    Timer listener = null;
    long timeout = 10000;
    Date next = null;

    /*
     * ------------------------------------------
     *  CONSTRUCTORS
     * ------------------------------------------
     */

    public TimerAlarmClock(Timer listener, long timeout) {
        this.listener = listener;
        this.timeout = Math.max(0L, timeout);
    }

    public TimerAlarmClock(Timer listener, Date next) {
        this.listener = listener;
        this.next = next;
    }

    /*
     * ------------------------------------------
     *  PUBLIC METHODS
     * ------------------------------------------
     */

    /**
     * This method is called by the timer when it is started.
     */
    public void run() {

        try {
            //this.sleep(timeout);
            TimerAlarmClockNotification notif = new TimerAlarmClockNotification(this);
            listener.notifyAlarmClock(notif);
        } catch (Exception e) {
            TIMER_LOGGER.logp(Level.FINEST, Timer.class.getName(), "run",
                    "Got unexpected exception when sending a notification", e);
        }
    }
}

⏎ javax/management/timer/TimerAlarmClock.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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