clear method
override
Removes all elements in the queue. The size of the queue becomes zero.
Implementation
void clear() {
if (_head != _tail) {
for (int i = _head; i != _tail; i = (i + 1) & (_table.length - 1)) {
_table[i] = null;
}
_head = _tail = 0;
_modificationCount++;
}
}