static byte[] getEmptyChunk(int leastLength) {
    if (emptyChunk.length >= leastLength) {
      return emptyChunk; // In most time
    }

    synchronized (CoderUtil.class) {
      emptyChunk = new byte[leastLength];
    }

    return emptyChunk;
  }
@Test
  public void testGetEmptyChunk() {
    byte[] ret = CoderUtil.getEmptyChunk(chunkSize);
    for (int i = 0; i < chunkSize; i++) {
      assertEquals(0, ret[i]);
    }
  }