@Override
  public String toString() {
    return MoreObjects.toStringHelper(this).add("blockCount", getBlockCount())
      .add("currentSize", StringUtils.byteDesc(getCurrentSize()))
      .add("freeSize", StringUtils.byteDesc(getFreeSize()))
      .add("maxSize", StringUtils.byteDesc(getMaxSize()))
      .add("heapSize", StringUtils.byteDesc(heapSize()))
      .add("minSize", StringUtils.byteDesc(minSize())).add("minFactor", minFactor)
      .add("multiSize", StringUtils.byteDesc(multiSize())).add("multiFactor", multiFactor)
      .add("singleSize", StringUtils.byteDesc(singleSize())).add("singleFactor", singleFactor)
      .toString();
  }
Eviction method. Evict items in order of use, allowing delete items which haven't been used for
the longest amount of time.
@return how many bytes were freed
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/LruAdaptiveBlockCache.java