JarFile open(final File jarFile) throws IOException {
  isTrue(jarFile.exists(),"The JAR file must exists.");
  return new JarFile(jarFile);
}

JarFile open ( final File jarFile ) throws IOException { isTrue ( jarFile . exists ( ) , "The JAR file must exists." ) ; return new JarFile ( jarFile ) ; }
opens the specified jar file and returns a valid handle .
