code: public static void addEntry(File zip, ZipEntrySource entry, File destZip) {
      addEntries(zip, new ZipEntrySource[] { entry }, destZip);
    }
docs: Copies an existing ZIP file and appends it with one new entry.
  
  @param zip
  an existing ZIP file (only read).
  @param entry
  new ZIP entry appended.
  @param destZip
  new ZIP file created.