I am doing a project in which I require btree or b+tree data structure. Does anyone know of an existing implementation of btree or b+tree (with insert, delete, search algorithms)? It should accept string as input and form btree or b+tree of these string.
In the lack of details about the problem that you need to solve, I am going to allow myself to suggest an alternative solution that might solve your problem: use a red/black tree instead.
The red/black tree can be thought of as a b-tree, as explained on Wikipedia:
A red-black tree is similar in structure to a B-tree of order 4, where each node can contain between 1 to 3 values and (accordingly) between 2 to 4 child pointers. In such B-tree, each node will contain only one value matching the value in a black node of the red-black tree, with an optional value before and/or after it in the same node, both matching an equivalent red node of the red-black tree [...]
Java has two built-in classes, TreeMap and TreeSet, providing red/black trees. None of these will take a string as input and grow a tree from it, but you might be able to implement something similar "around" one of those classes.
jdbm has a very solid implementation of b+tree. Also h+tree which is an interesting related data structure.
I've had to implement my own and open sourced the code.
You could try Electric's BTree (author page here).
来源：https://stackoverflow.com/questions/2574661/existing-implementation-of-btree-or-btree-in-java