@Override
  public final Iterator<List<HStoreFile>> iterator() {
    return new Iterator<List<HStoreFile>>() {
      private int nextIndex = 0;

      @Override
      public boolean hasNext() {
        return nextIndex < fileSizes.length;
      }

      @Override
      public List<HStoreFile> next() {
        List<HStoreFile> files = createStoreFileList(fileSizes[nextIndex]);
        nextIndex += 1;
        return files;
      }

      @Override
      public void remove() {
      }
    };
  }
The explicit files size lists to return.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/compactions/ExplicitFileListGenerator.java