public interface Buffer<T>
int
capacity()
void
clear()
T
dequeue()
dropHead()
dropTail()
enqueue(T elem)
boolean
isEmpty()
isFull()
nonEmpty()
peek()
used()
int capacity()
int used()
boolean isFull()
boolean isEmpty()
boolean nonEmpty()
void enqueue(T elem)
T dequeue()
T peek()
void clear()
void dropHead()
void dropTail()