code: @SuppressWarnings({ "unchecked", "rawtypes" })
      boolean add(PoolArena<?> area, PoolChunk chunk, ByteBuffer nioBuffer,
                  long handle, int normCapacity, SizeClass sizeClass) {
          MemoryRegionCache<?> cache = cache(area, normCapacity, sizeClass);
          if (cache == null) {
              return false;
          }
          return cache.add(chunk, nioBuffer, handle);
      }
docs: Add {@link PoolChunk} and {@code handle} to the cache if there is enough room.
  Returns {@code true} if it fit into the cache {@code false} otherwise.