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/annotation/processing/SupportedOptions.java

/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package javax.annotation.processing;

import java.lang.annotation.*;
import static java.lang.annotation.RetentionPolicy.*;
import static java.lang.annotation.ElementType.*;

/**
 * An annotation used to indicate what options an annotation processor
 * supports.  The {@link Processor#getSupportedOptions} method can
 * construct its result from the value of this annotation, as done by
 * {@link AbstractProcessor#getSupportedOptions}.  Only {@linkplain
 * Processor#getSupportedOptions strings conforming to the
 * grammar} should be used as values.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ahé
 * @since 1.6
 */
@Documented
@Target(TYPE)
@Retention(RUNTIME)
public @interface SupportedOptions {
    /**
     * Returns the supported options.
     * @return the supported options
     */
    String [] value();
}

⏎ javax/annotation/processing/SupportedOptions.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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