private static <T> LoadingCache<Class<T>, AtomicInteger> createCache() {
    return CacheBuilder.newBuilder().build(new CacheLoader<>() {
      @Override
      public AtomicInteger load(Class<T> key) throws Exception {
        return new AtomicInteger();
      }
    });
  }
A global compressor/decompressor pool used to save and reuse (possibly native)
compression/decompression codecs. Copied from the class of the same name in hadoop-common and
augmented to improve borrow/return performance.
hbase-common/src/main/java/org/apache/hadoop/hbase/io/compress/CodecPool.java