Java 'ext' directory versus -Xbootclasspath/p:
<p>I want to make use of the JSR166 facilities in Java 6. So I've downloaded the jar.</p>

<p>I'd like to make this process (relatively) painless. I was perplexed to discover that adding it to the ext directory in my Mac's JDK/JRE (or to /Library/Java/extensions) did not work.</p>

<p>Only -Xbootclasspath did the trick.</p>

<p>Why is this? Are exts somehow defined more narrowly?</p>
