Create a pure identifier that is unique with respect to the
host on which it is generated. This UID is unique under the
following conditions: a) the machine takes more than one second
to reboot, and b) the machine's clock is never set backward.
In order to construct a UID that is globally unique, simply
pair a UID with an InetAddress.
public UID(short num)
Create a "well-known" ID. There are 2^16 -1 such possible
well-known ids. An id generated via this constructor will not
clash with any id generated via the default UID
constructor which will generates a genuinely unique identifier
with respect to this host.