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/Refreshable.java

/*
 * Copyright (c) 1999, 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;

/**
 * Objects such as credentials may optionally implement this
 * interface to provide the capability to refresh itself.
 * For example, a credential with a particular time-restricted lifespan
 * may implement this interface to allow callers to refresh the time period
 * for which it is valid.
 *
 * @see javax.security.auth.Subject
 */
public interface Refreshable {

    /**
     * Determine if this {@code Object} is current.
     *
     * <p>
     *
     * @return true if this {@code Object} is currently current,
     *          false otherwise.
     */
    boolean isCurrent();

    /**
     * Update or extend the validity period for this
     * {@code Object}.
     *
     * <p>
     *
     * @exception SecurityException if the caller does not have permission
     *          to update or extend the validity period for this
     *          {@code Object}. <p>
     *
     * @exception RefreshFailedException if the refresh attempt failed.
     */
    void refresh() throws RefreshFailedException;
}

⏎ javax/security/auth/Refreshable.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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