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/naming/StringRefAddr.java

/*
 * Copyright (c) 1999, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.naming;

/**
 * This class represents the string form of the address of
 * a communications end-point.
 * It consists of a type that describes the communication mechanism
 * and a string contents specific to that communication mechanism.
 * The format and interpretation of
 * the address type and the contents of the address are based on
 * the agreement of three parties: the client that uses the address,
 * the object/server that can be reached using the address, and the
 * administrator or program that creates the address.
 *
 * <p> An example of a string reference address is a host name.
 * Another example of a string reference address is a URL.
 *
 * <p> A string reference address is immutable:
 * once created, it cannot be changed.  Multithreaded access to
 * a single StringRefAddr need not be synchronized.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 *
 * @see RefAddr
 * @see BinaryRefAddr
 * @since 1.3
 */

public class StringRefAddr extends RefAddr {
    /**
     * Contains the contents of this address.
     * Can be null.
     * @serial
     */
    private String contents;
    /**
      * Constructs a new instance of StringRefAddr using its address type
      * and contents.
      *
      * @param addrType A non-null string describing the type of the address.
      * @param addr The possibly null contents of the address in the form of a string.
      */
    public StringRefAddr(String addrType, String addr) {
        super(addrType);
        contents = addr;
    }

    /**
      * Retrieves the contents of this address. The result is a string.
      *
      * @return The possibly null address contents.
      */
    public Object getContent() {
        return contents;
    }

    /**
     * Use serialVersionUID from JNDI 1.1.1 for interoperability
     */
    private static final long serialVersionUID = -8913762495138505527L;
}

⏎ javax/naming/StringRefAddr.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

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)