The com.sun.jarsigner package will be deprecated in JDK-8076535. This includes the ContentSigner class, the ContentSignerParameters interface, and the jarsigner command's "-altsigner" and "-altsignerpath" options.

If two versions of the jarsigner manual will be published for JDK 9 (as they were for JDK 8), both should be updated.

JDK 8 versions, for reference:
http://docs.oracle.com/javase/8/docs/technotes/tools/unix/jarsigner.html
http://docs.oracle.com/javase/8/docs/technotes/tools/windows/jarsigner.html