synchronized void clear() {
    checkConsumer();

    for (int i = data.length; i-- > 0; ) {
      data[i] = null;
    }
    size = 0;
  }
@Test public void testClear() {
    final SinkQueue<Integer> q = new SinkQueue<Integer>(128);
    for (int i = 0; i < q.capacity() + 97; ++i) {
      q.enqueue(i);
    }
    assertEquals("queue size", q.capacity(), q.size());
    q.clear();
    assertEquals("queue size", 0, q.size());
  }