$30.$ As discussed in this section, instead of having our queue methods throw exceptions

in the case of $$erroneous$$ invocations, we could have the queue methods handle the

situation themselves. We deine the following two $$safe$$ methods:

$$ boolean safeEnqueue $($T element$)$ adds element to the rear of the

queue; returns true if element successfully added, false otherwise

$$ T safeDequeue $()$ returns null if this queue is empty; otherwise removes

front element from this queue and returns i