java.util.concurrent.ConcurrentSkipListMap#size ( )源码实例Demo

/**
 * Gets the start {@link Offset} of the given instance of  {@code indexSegments}.
 * @param indexSegments the map of index segment start {@link Offset} to {@link IndexSegment} instances
 */
private Offset getStartOffset(ConcurrentSkipListMap<Offset, IndexSegment> indexSegments) {
  Offset startOffset;
  if (indexSegments.size() == 0) {
    LogSegment firstLogSegment = log.getFirstSegment();
    startOffset = new Offset(firstLogSegment.getName(), firstLogSegment.getStartOffset());
  } else {
    startOffset = indexSegments.firstKey();
  }
  return startOffset;
}
 

/**
 * Gets the end {@link Offset} of the given instance of {@code indexSegments}.
 * @param indexSegments the map of index segment start {@link Offset} to {@link IndexSegment} instances
 */
private Offset getCurrentEndOffset(ConcurrentSkipListMap<Offset, IndexSegment> indexSegments) {
  // If no indexSegments exist, return start offset of first log segment
  return indexSegments.size() == 0 ? getStartOffset(indexSegments)
      : indexSegments.lastEntry().getValue().getEndOffset();
}