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/MBeanServerDelegateMBean.java

/*
 * Copyright (c) 1999, 2003, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.management;


/**
 * Defines the management interface  of an object of class MBeanServerDelegate.
 *
 * @since 1.5
 */
public interface MBeanServerDelegateMBean   {

    /**
     * Returns the MBean server agent identity.
     *
     * @return the agent identity.
     */
    public String getMBeanServerId();

    /**
     * Returns the full name of the JMX specification implemented
     * by this product.
     *
     * @return the specification name.
     */
    public String getSpecificationName();

    /**
     * Returns the version of the JMX specification implemented
     * by this product.
     *
     * @return the specification version.
     */
    public String getSpecificationVersion();

    /**
     * Returns the vendor of the JMX specification implemented
     * by this product.
     *
     * @return the specification vendor.
     */
    public String getSpecificationVendor();

    /**
     * Returns the JMX implementation name (the name of this product).
     *
     * @return the implementation name.
     */
    public String getImplementationName();

    /**
     * Returns the JMX implementation version (the version of this product).
     *
     * @return the implementation version.
     */
    public String getImplementationVersion();

    /**
     * Returns the JMX implementation vendor (the vendor of this product).
     *
     * @return the implementation vendor.
     */
    public String getImplementationVendor();

}

⏎ javax/management/MBeanServerDelegateMBean.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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