static Node alloc() {
final int threshold = 2;
int tryCnt = 0;
while (true) {
tryCnt++;
Node n = pool.poll();
if (n == null) {
return new Node();
} else {
if (n.getRefCnt() > 0) {
pool.add(n);
if (tryCnt <= threshold) continue;
else return new Node();
} else {
if (n.next != null) n.next.decRefCnt();
n.init();
return n;
}
}
}
}
static void free(Node n) {
pool.add(n);
}