<p>I'm trying to save the output of an vector image drawin in Java2D to an SWF file. There are great libraries for saving java2D output as things like SVG (BATIK) and PDF(itext) but I can't find one for SWF.  Any ideas?</p>

Flash generally uses SVG as its native format.  You could export to SVG and then write a trivial Flash program to embed and display the image.  But why use Flash at all?  Most browsers are capable of displaying SVG nowadays.
Edit
: I don't know why I was downvoted for a clearly correct answer.  I can understand not being upvoted for not having the best answer (I fully acknowledge that this soltuion isn't ideal), but I really don't think it deserves a downvote.  You can consult the section in the middle of
this page
about embedding SVG in Flex programs.  For those of you who aren't familiar, Flex is an adobe toolkit/library that generates SWF programs that run in the normal Flash player.  Many (all?) of the normal Flash libraries are available to it.  It uses ActionScript.  For you doubters, here's a snippet showing exactly how you do it, copied from a Flex program I wrote.  It should go inside an MXML file.
```
```
<mx:Script><![CDATA[

[Embed(source="../images/down.svg")]
[Bindable]
protected var drillDownImage:Class;

]]></mx:Script>

<mx:HBox width="50%" horizontalAlign="right">
    <mx:Image id="drillDownButton" source="{drillDownImage}" height="20" width="20" click="drillDown();" />
</mx:HBox>
```
```
Now all you need to do is wrap that in an appropriate MXML file, maybe import some controls packages for the HBox and Image tags, and you're good to go.  The example in the link I provided should be sufficient for you to figure it out.