B+Tree on-disk implementation in Java

Question

Does anyone know where to find a B+Tree on-disk implementation? I went through google forward and backward and unfortunately I couldn't find anything sensible. Other threads have suggested to maybe take the tree from sqlite, sqljet or bdb but these trees are nested in the whole database and you can't really "just" filter out the B+Tree. I'm really looking for only a on-disk B+Tree... without any fancy things around.

Answer 1

There is a GDBM-inspired Java persistence engine: MapDB

Answer 2

I've implemented disk-based B+-tree in the past. https://github.com/myui/xbird/blob/master/xbird-open/main/src/java/xbird/storage/index/BIndexFile.java

Find usage in https://github.com/myui/xbird/blob/master/xbird-open/main/test/java/xbird/storage/index/BIndexMultiValueFileTest.java