BSTs

In a binary tree every node has an optional left, and optional right child node. A BST(binary search tree) is a binary tree that satsifies the following properties:
1) Every node has a unique VALUE
2) The VALUE at a given node must be greater than the VALUE at every node in its left subtree
3) The VALUE at a given node must be less than the VALUE at every node in its right subtree
A set of VALUEs can have multiple BSTs associated with it depending on how the nodes are arranged. For example:
values = {3,2,1}

  1      |  1    |    2    |      3  |    3                     
   \     |   \   |   / \   |     /   |   /      
    2    |    3  |  1   3  |    2    |  1         
     \   |   /   |         |   /     |   \                   
      3  |  2    |         |  1      |    2                 

The set {3,2,1} has 5 possible BSTs shown above. Two BSTs are different if they differ in the position of at least one VALUE. Given a set of VALUEs you will determine how many BSTs are possible. Create a class BSTs that contains the method howMany, which takes an int[] values, and returns an int that represents the number of distinct possible BSTs resulting from the given set of values.