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/type/IntersectionType.java

/*
 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.lang.model.type;

import java.util.List;

/**
 * Represents an intersection type.
 *
 * <p>An intersection type can be either implicitly or explicitly
 * declared in a program. For example, the bound of the type parameter
 * {@code <T extends Number & Runnable>} is an (implicit) intersection
 * type.  As of {@link javax.lang.model.SourceVersion#RELEASE_8
 * RELEASE_8}, this is represented by an {@code IntersectionType} with
 * {@code Number} and {@code Runnable} as its bounds.
 *
 * @implNote Also as of {@link
 * javax.lang.model.SourceVersion#RELEASE_8 RELEASE_8}, in the
 * reference implementation an {@code IntersectionType} is used to
 * model the explicit target type of a cast expression.
 *
 * @since 1.8
 */
public interface IntersectionType extends TypeMirror {

    /**
     * Return the bounds comprising this intersection type.
     *
     * @return the bounds of this intersection types.
     */
    List<? extends TypeMirror> getBounds();
}

⏎ javax/lang/model/type/IntersectionType.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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