Convert sorted linkedlist into balanced binary search tree
I'm going to post a simpler review than I would if I fully understood this class, but hopefully if you clarify some things, I (or others) can come back and review it more in-depth.

My main problem with this code, is that I don't know what it is trying to do. The class is called SortedLinkedListToBalancedBST, which makes me think that it is some kind of converter utility class. However, the class itself has a private member of TreeNode&lt;T&gt; and doesn't have any public methods which are static or return some kind of BST, so that makes me think that it is just a BST implementation which happens to know how to create a BST from a Linked List. But the class doesn't even have all the functionality of a BST!

You need to decide what this class is going to be and then name it appropriately. Is it a class which knows how to convert from a Linked List to a BST and vice-versa, or is it a BST which knows how to create a BST from a Linked List? (The current name isn't even really all encompassing since the class can get the Linked List from the BST as well.)

Without a better understanding of the purpose of this class, I can't comment on the functionality and implementation, but I can talk about the style:


Give your variables better names. ll, lb, and hb are not good names. linkedList is a better name for ll, and for the others, I honestly have no clue what they even are supposed to represent.
Give different methods different names. Your two inorder() methods do two completely different things. One adds items to a List. The other gets a tree from an ordered list.
convert() seems like it might be more appropriate as a constructor.