final class BinaryNode
{
    BinaryNode( )
    {
        this( null );
    }

    BinaryNode( Object theElement )
    {
        this( theElement, null, null );
    }

    BinaryNode( Object theElement, BinaryNode lt, BinaryNode rt )
    {
        element = theElement;
        left    = lt;
        right   = rt;
    }

    /**
     * Return the size of the binary tree rooted at t.
     */
    static int size( BinaryNode t )
    {
        if( t == null )
            return 0;
        else
            return 1 + size( t.left ) + size( t.right );
    }

    /**
      * Return the height of the binary tree rooted at t.
      */
    static int height( BinaryNode t )
    {
        if( t == null )
            return -1;
        else
            return 1 + Math.max( height( t.left ), height( t.right ) );
    }

    void printPreOrder( )
    {
        System.out.println( element );       // Node
        if( left != null )
            left.printPreOrder( );           // Left
        if( right != null )
            right.printPreOrder( );          // Right
    }


    void printPostOrder( )
    {
        if( left != null )
            left.printPostOrder( );          // Left
        if( right != null )
            right.printPostOrder( );         // Right
        System.out.println( element );       // Node
    }

    void printInOrder( )
    {
        if( left != null )
            left.printInOrder( );            // Left
        System.out.println( element );       // Node
        if( right != null )
            right.printInOrder( );           // Right
    }


    /**
     * Return a reference to a node that is the root of a
     * duplicate of the binary tree rooted at the current node.
     */
    BinaryNode duplicate( )
    {
        BinaryNode root = new BinaryNode( element );

        if( left != null )            // If there's a left subtree
            root.left = left.duplicate( );    // Duplicate; attach
        if( right != null )          // If there's a right subtree
            root.right = right.duplicate( );  // Duplicate; attach
        return root;                      // Return resulting tree
    }


    // Friendly data; accessible by other package routines
    Object     element;
    BinaryNode left;
    BinaryNode right;
}