acquire method
T
acquire()
Hands out a reusable T — an existing free one if available,
otherwise a freshly created one. Always succeeds; maxCapacity
bounds what release retains, not what acquire can hand out.
Implementation
T acquire() {
final item = _free.isNotEmpty ? _free.removeLast() : _createNew();
_active.add(item);
if (_active.length > _peakActive) _peakActive = _active.length;
return item;
}