code: void removeEQ(Object o) {
          final ReentrantLock lock = this.lock;
          lock.lock();
          try {
              for (Iterator<E> it = q.iterator(); it.hasNext(); ) {
                  if (o == it.next()) {
                      it.remove();
                      break;
                  }
              }
          } finally {
              lock.unlock();
          }
      }
docs: Identity-based version for use in Itr.remove.