Returns the hashCode. If the {@link #getId() id} is not {@code null}, its hashcode is returned immediately.
If it is {@code null}, an attributes-based hashCode will be calculated and returned.
<p/>
Do your best to ensure {@code SimpleSession} instances receive an ID very early in their lifecycle to
avoid the more expensive attributes-based calculation.
Returns the hashCode. If the {@link #getId() id} is not {@code null}, its hashcode is returned immediately. If it is {@code null}, an attributes-based hashCode will be calculated and returned. <p/> Do your best to ensure {@code SimpleSession} instances receive an ID very early in their lifecycle to avoid the more expensive attributes-based calculation.
@return this object's hashCode