Sets an application's URLStreamHandlerFactory. This method can be called at most once in a given Java Virtual Machine.

The URLStreamHandlerFactory instance is used to construct a stream protocol handler from a protocol name.

If there is a security manager, this method first calls the security manager's checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

Parameters:

fac the desired factory.

Exceptions:

Error if the application has already set a factory.

SecurityException if a security manager exists and its checkSetFactory method doesn't allow the operation.

`Error`		if the application has already set a factory.
`SecurityException`		if a security manager exists and its `checkSetFactory` method doesn't allow the operation.