If you don't want to confuse people when you sign your e-mail, make sure you're using PGP/MIME not inline signing. I've been signing my mail for years and had almost zero problems doing this.
I read "Solve the problem in a single separate .java file which compiles and runs with JDK 6 or 7." to mean that the entire solution has to be in one Java file.
And even if this endpoint (defined in the WSDL) was changed to to https there is nothing stopping you from overriding it and pointing it to any other (possibly unsecure) URL.
