A B+ tree is an n-ary tree with a variable but often large number of children per node. A B+ tree consists of a root, internal nodes and leaves. (Link->http://ift.tt/1xK6Dtf)
A B+ tree can be viewed as a B-tree (Link->http://ift.tt/1xK6Bl6) in which each node contains only keys (not key-value pairs), and to which an additional level is added at the bottom with linked leaves.
The primary value of a B+ tree is in storing data for efficient retrieval in a (Link->http://ift.tt/1xK6Bl8) typically on the order of 100 or more), which reduces the number of I/O operations required to find an element in the tree.
The main idea of using B-Trees is to reduce the number of disk accesses. Most of the tree operations (search, insert, delete, max, min, ..etc ) require O(h) disk accesses where h is height of the tree. B-tree is a fat tree. Height of B-Trees is kept low by putting maximum possible keys in a B-Tree node. Generally, a B-Tree node size is kept equal to the disk block size.
Does Java pass by reference or pass by value? | JavaWorld
Java manipulates objects 'by reference,' but it passes object references to methods 'by value.'" As a result, you cannot write a standard swap method to swap objects