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/callback/Callback.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.callback;

/**
 * <p> Implementations of this interface are passed to a
 * {@code CallbackHandler}, allowing underlying security services
 * the ability to interact with a calling application to retrieve specific
 * authentication data such as usernames and passwords, or to display
 * certain information, such as error and warning messages.
 *
 * <p> {@code Callback} implementations do not retrieve or
 * display the information requested by underlying security services.
 * {@code Callback} implementations simply provide the means
 * to pass such requests to applications, and for applications,
 * if appropriate, to return requested information back to the
 * underlying security services.
 *
 * @see javax.security.auth.callback.CallbackHandler
 * @see javax.security.auth.callback.ChoiceCallback
 * @see javax.security.auth.callback.ConfirmationCallback
 * @see javax.security.auth.callback.LanguageCallback
 * @see javax.security.auth.callback.NameCallback
 * @see javax.security.auth.callback.PasswordCallback
 * @see javax.security.auth.callback.TextInputCallback
 * @see javax.security.auth.callback.TextOutputCallback
 */
public interface Callback { }

⏎ javax/security/auth/callback/Callback.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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