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 java.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ java/awt/image/renderable/RenderedImageFactory.java

/*
 * Copyright (c) 1998, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
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 */

/* ********************************************************************
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 *** COPYRIGHT (c) Eastman Kodak Company, 1997                      ***
 *** As  an unpublished  work pursuant to Title 17 of the United    ***
 *** States Code.  All rights reserved.                             ***
 **********************************************************************
 **********************************************************************
 **********************************************************************/

package java.awt.image.renderable;
import java.awt.image.RenderedImage;
import java.awt.RenderingHints;

/**
 * The RenderedImageFactory interface (often abbreviated RIF) is
 * intended to be implemented by classes that wish to act as factories
 * to produce different renderings, for example by executing a series
 * of BufferedImageOps on a set of sources, depending on a specific
 * set of parameters, properties, and rendering hints.
 */
public interface RenderedImageFactory {

  /**
   * Creates a RenderedImage representing the results of an imaging
   * operation (or chain of operations) for a given ParameterBlock and
   * RenderingHints.  The RIF may also query any source images
   * referenced by the ParameterBlock for their dimensions,
   * SampleModels, properties, etc., as necessary.
   *
   * <p> The create() method can return null if the
   * RenderedImageFactory is not capable of producing output for the
   * given set of source images and parameters.  For example, if a
   * RenderedImageFactory is only capable of performing a 3x3
   * convolution on single-banded image data, and the source image has
   * multiple bands or the convolution Kernel is 5x5, null should be
   * returned.
   *
   * <p> Hints should be taken into account, but can be ignored.
   * The created RenderedImage may have a property identified
   * by the String HINTS_OBSERVED to indicate which RenderingHints
   * were used to create the image.  In addition any RenderedImages
   * that are obtained via the getSources() method on the created
   * RenderedImage may have such a property.
   *
   * @param paramBlock a ParameterBlock containing sources and parameters
   *        for the RenderedImage to be created.
   * @param hints a RenderingHints object containing hints.
   * @return A RenderedImage containing the desired output.
   */
  RenderedImage create(ParameterBlock paramBlock,
                       RenderingHints hints);
}

⏎ java/awt/image/renderable/RenderedImageFactory.java

Or download all of them as a single archive file:

File name: jre-rt-java-1.8.0_191-src.zip
File size: 6664831 bytes
Release date: 2018-10-28
Download 

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