The classes for the Java2D(TM) demo are contained in the J2Ddemo.jar file.  

To run the J2D demo:

% java -jar J2Ddemo.jar

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Introduction

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This Java2D demo consists of a set of demos housed in one GUI 

framework that uses a JTabbedPane.  You can access different groups of 

demos by clicking the tabs at the top of the pane. There are demo 

groups for Arcs_Curves, Clipping, Colors, Composite, Fonts, Images, 

Lines, Mix, Paint, Paths and Transforms.  On the right-hand side of the 

pane, the GUI framework features individual and global controls for 

changing graphics attributes. There's also a memory-usage monitor, and 

a monitor for tracking the performance, in frames per second, of 

animation demos.

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Tips on usage 

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Click on one of the tabs at the top of the pane to select a demo group.  

When you select a group, a set of surfaces is displayed, each of which 

contains one of the group's demos. At the bottom of each surface is 

a set of tools for controlling the demo.  The tools can be displayed

by selecting the Tools checkbox in the Global Controls panel or

by clicking on the slim strip of gray bumps at the bottom of the demo

panel.

If you click on a demo surface, that demo is laid out by itself. A

new icon button will appear in the demo's tools toolbar one that enables 

you to create new instances of that demo's surface. 

To run the demo continuously without user interaction, select the 

Run Window item in the Options menu and press the run button in the 

new window that's displayed.  To do this from the command line:

    java -jar J2Ddemo.jar -runs=10

To view all the command line options for customizing demo runs:

    java -jar J2Ddemo.jar -help

You can run the demos in stand-alone mode by issuing a command like this

    java -cp J2Ddemo.jar java2d.demos.Clipping.ClipAnim

You can run the demos in groups by issuing a command like this

    java -cp J2Ddemo.jar java2d.DemoGroup Clipping    

To increase or decrease the Memory Monitor sampling rate click on the

Memory Monitor's title border, a panel with a TextField will appear.

The J2Ddemo Intro (the 'J2D demo' tab) contains a scene table, click in 

the gray border and a table will appear.

Animated demos have a slider to control the animation rate.  Bring up

the animated demo toolbar, then click in the gray area of the toolbar

panel, the toolbar goes away and the slider appears.

Demos that have Custom Controls can have their Custom Control Thread

activated and stopped by clicking in the gray area of the demos Custom 

Control panel.

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NOTE about demo surfaces 

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The demo groups are in separate packages with their class files stored 

in directories named according to the demo group name.  All drawing 

demos extend either the Surface, AnimatingSurface, ControlsSurface or

AnimatingControlsSurface classes.  Surface is the base class, demos

must implement the Surface's render method.  All animated demos extend 

either the AnimatingSurface or the AnimatingControlsSurface classes.  

Animated demos must implement the reset and step methods.  The demos

with gui controls extend either the ControlsSurface or the 

AnimatingControlsSurface classes.  Demos with controls must implement

the methods in the CustomControlsContext interface.

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Here are some resources for learning about and using the Java2D(TM)

OpenJDK group page: http://openjdk.java.net/groups/2d/

Learning Java 2D: http://www.oracle.com/technetwork/articles/java/java2dpart1-137217.html

Tutorial : http://download.oracle.com/javase/tutorial/2d/

Specification: http://download.oracle.com/javase/8/docs/technotes/guides/2d/spec/j2d-bookTOC.html

Java 2D (TM) API White Paper : http://www.oracle.com/technetwork/java/javase/tech/2d-142228.html

2D FAQ: http://www.oracle.com/technetwork/java/index-137037.html