Binary Tree

/**

* BinaryTree is a simple binary search tree that stores unique int values.

*

* For every node, all values in its left subtree are smaller and all values

* in its right subtree are larger. Duplicate values are ignored.

*

* The tree supports:

* - insert(int): adds a value (the first value becomes the root)

* - contains(int): checks whether a value is stored in the tree

* - inorder(): prints all values in ascending order

*

* Internally, the tree consists of BinaryNode objects (a private static

* inner class). Each node holds one value and references to its left and

* right child. The tree class itself only keeps a reference to the root and

* delegates the work to the nodes, which solve it recursively.

*/