@Override
  public boolean add(TsFileResource newNode) {
    if (newNode.prev != null || newNode.next != null) {
      // this node already in a list
      return false;
    }
    if (tail == null) {
      header = newNode;
      tail = newNode;
      count++;
    } else {
      insertAfter(tail, newNode);
    }
    return true;
  }
Insert a new tsFileResource node to the end of List
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/tsfile/TsFileResourceList.java