code: private Object discardFromBucket(int bucketIndex, int entryIndex) {
          numDiscards++;
          bucketSizes[bucketIndex]--;
          numEntries--;
          return values[bucketIndex][entryIndex];
      }
docs: Discard an entry from the specified bucket. The actual entry is not nulled out because
  it will later be overwritten.
  
  @param bucketIndex the index of the bucket from which to discard an entry.
  @param entryIndex the index of the entry within the bucket to discard.
  
  @return the discarded value.