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/lang/model/package-info.java

/*
 * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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/**
 * Classes and hierarchies of packages used to model the Java
 * programming language.
 *
 * The members of this package and its subpackages are for use in
 * language modeling and language processing tasks and APIs including,
 * but not limited to, the {@linkplain javax.annotation.processing
 * annotation processing} framework.
 *
 * <p> This language model follows a <i>mirror</i>-based design; see
 *
 * <blockquote>
 * Gilad Bracha and David Ungar. <i>Mirrors: Design Principles for
 * Meta-level Facilities of Object-Oriented Programming Languages</i>.
 * In Proc. of the ACM Conf. on Object-Oriented Programming, Systems,
 * Languages and Applications, October 2004.
 * </blockquote>
 *
 * In particular, the model makes a distinction between static
 * language constructs, like the {@linkplain javax.lang.model.element
 * element} representing {@code java.util.Set}, and the family of
 * {@linkplain javax.lang.model.type types} that may be associated
 * with an element, like the raw type {@code java.util.Set}, {@code
 * java.util.Set<String>}, and {@code java.util.Set<T>}.
 *
 * <p> Unless otherwise specified, methods in this package will throw
 * a {@code NullPointerException} if given a {@code null} argument.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @since 1.6
 */

package javax.lang.model;

⏎ javax/lang/model/package-info.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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