Sets the authenticator that will be used by the networking code when a proxy or an HTTP server asks for authentication.

First, if there is a security manager, its checkPermission method is called with a NetPermission("setDefaultAuthenticator") permission. This may result in a java.lang.SecurityException.

Parameters:

a The authenticator to be set. If a is null then any previously set authenticator is removed.

Exceptions:

SecurityException if a security manager exists and its checkPermission method doesn't allow setting the default authenticator.