javadoc can not generate localized html file because of that words are hardcoded in the source.

out.println("<h2> Java API Packages </h2>");
out.println("<h2> Other Packages </h2>");
out.println("<li> package " + pkgString(pkg, s));

Refer URL
http://SunSITE.sut.ac.jp/java/javaj/japi/packages.html
as an example to see what their expectation is.