http://ant.apache.org/manual/CoreTasks/javadoc.html
1.) extract JUnit source code to c:\temp\src
2.) create an ANT build.xml file to run the JavaDoc task as follows
<?xml version="1.0" ?>
<project name="JavaDocs" default="doc">
<target name="doc">
<javadoc destdir="docs/api"
sourcepath="src"
packagenames="junit.*"
windowtitle="JUnit"
/>
</target>
</project>3.) save the build.xml file in c:\temp
4.) run c:\temp>ant
Another example ... To get JavaDocs for the Time And Money library available from SourceForge,
<target name="doc">
<javadoc destdir="docs/api"
sourcepath="src"
packagenames="com.domainlanguage.*"
windowtitle="TimeAndMoney"
/>
</target>