code: private void checkTreeBin(int index) {
      long tb = treeBins[index];
  
      boolean empty = (treeMap & (1 << index)) == 0;
      if (tb == -1 && !empty) {
        throw new AssertionError("Tree " + index + " is marked as occupied but has an invalid head pointer");
      }
      if (!empty) {
        checkTree(tb);
      }
    }
docs: /*  Check all the chunks in a treebin.