static ReusableIF checkout() {
if (head == null) {
created++;
return new Reusable();
} else {
held--;
ReusableIF tmp = head;
head = head.link;
tmp.reset();
return tmp;
}
}
static void checkin(ReusableIF reusable) {
held++;
reusable.link = head;
head = reusable;
}