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/security/auth/login/ConfigurationSpi.java

/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.security.auth.login;

/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the {@code Configuration} class.
 * All the abstract methods in this class must be implemented by each
 * service provider who wishes to supply a Configuration implementation.
 *
 * <p> Subclass implementations of this abstract class must provide
 * a public constructor that takes a {@code Configuration.Parameters}
 * object as an input parameter.  This constructor also must throw
 * an IllegalArgumentException if it does not understand the
 * {@code Configuration.Parameters} input.
 *
 *
 * @since 1.6
 */

public abstract class ConfigurationSpi {
    /**
     * Retrieve the AppConfigurationEntries for the specified <i>name</i>.
     *
     * <p>
     *
     * @param name the name used to index the Configuration.
     *
     * @return an array of AppConfigurationEntries for the specified
     *          <i>name</i>, or null if there are no entries.
     */
    protected abstract AppConfigurationEntry[] engineGetAppConfigurationEntry
                                                        (String name);

    /**
     * Refresh and reload the Configuration.
     *
     * <p> This method causes this Configuration object to refresh/reload its
     * contents in an implementation-dependent manner.
     * For example, if this Configuration object stores its entries in a file,
     * calling {@code refresh} may cause the file to be re-read.
     *
     * <p> The default implementation of this method does nothing.
     * This method should be overridden if a refresh operation is supported
     * by the implementation.
     *
     * @exception SecurityException if the caller does not have permission
     *          to refresh its Configuration.
     */
    protected void engineRefresh() { }
}

⏎ javax/security/auth/login/ConfigurationSpi.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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