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/lang/management/PlatformManagedObject.java

/*
 * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.lang.management;

import javax.management.ObjectName;

/**
 * A platform managed object is a {@linkplain javax.management.MXBean JMX MXBean}
 * for monitoring and managing a component in the Java platform.
 * Each platform managed object has a unique
 * <a href="ManagementFactory.html#MXBean">object name</a>
 * for the {@linkplain ManagementFactory#getPlatformMBeanServer
 * platform MBeanServer} access.
 * All platform MXBeans will implement this interface.
 *
 * <p>
 * Note:
 * The platform MXBean interfaces (i.e. all subinterfaces
 * of {@code PlatformManagedObject}) are implemented
 * by the Java platform only.  New methods may be added in these interfaces
 * in future Java SE releases.
 * In addition, this {@code PlatformManagedObject} interface is only
 * intended for the management interfaces for the platform to extend but
 * not for applications.
 *
 * @see ManagementFactory
 * @since 1.7
 */
public interface PlatformManagedObject {
    /**
     * Returns an {@link ObjectName ObjectName} instance representing
     * the object name of this platform managed object.
     *
     * @return an {@link ObjectName ObjectName} instance representing
     * the object name of this platform managed object.
     */
    public ObjectName getObjectName();
}

⏎ java/lang/management/PlatformManagedObject.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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