Inserts the specified element into this queue if it is possible to do
so immediately without violating capacity restrictions.
When using a capacity-restricted queue, this method is generally
add, which can fail to insert an element only
by throwing an exception.
|the element to add|
true if the element was added to this queue, else
|if the class of the specified element prevents it from being added to this queue|
|if the specified element is null and this queue does not permit null elements|
|if some property of this element prevents it from being added to this queue|