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/PrintJob.java

/*
 * Copyright (c) 1996, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.awt;

/**
 * An abstract class which initiates and executes a print job.
 * It provides access to a print graphics object which renders
 * to an appropriate print device.
 *
 * @see Toolkit#getPrintJob
 *
 * @author      Amy Fowler
 */
public abstract class PrintJob {

    /**
     * Gets a Graphics object that will draw to the next page.
     * The page is sent to the printer when the graphics
     * object is disposed.  This graphics object will also implement
     * the PrintGraphics interface.
     * @see PrintGraphics
     */
    public abstract Graphics getGraphics();

    /**
     * Returns the dimensions of the page in pixels.
     * The resolution of the page is chosen so that it
     * is similar to the screen resolution.
     */
    public abstract Dimension getPageDimension();

    /**
     * Returns the resolution of the page in pixels per inch.
     * Note that this doesn't have to correspond to the physical
     * resolution of the printer.
     */
    public abstract int getPageResolution();

    /**
     * Returns true if the last page will be printed first.
     */
    public abstract boolean lastPageFirst();

    /**
     * Ends the print job and does any necessary cleanup.
     */
    public abstract void end();

    /**
     * Ends this print job once it is no longer referenced.
     * @see #end
     */
    public void finalize() {
        end();
    }

}

⏎ java/awt/PrintJob.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 

⇒ JRE 8 rt.jar - javax.* Package Source Code

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