@Override
    public boolean hasNext() {
      return currentIndex >= 0;
    }
insert tsFileResource to a target pos(targetPos = index) e.g. if index = 0, then to the first,
if index = 1, then to the second.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/tsfile/TsFileResourceList.java