===============================================================================
Steps [8] through [12] (atop [0] through [7])
===============================================================================
   
class Problem7
+--------------------------------------------------------------[10]-+
|      +---+      +---+      +----+     +---+      +---+      +---+ |
| args | *-+-+ F1 | * |   F2 |null|  B1 | * |   B2 | * |   B3 | ? | |
|      +---+ |    +-+-+      +-+--+     +-+-+      +-+-+      +---+ |
+------------+------+----------+----------+----------+--------------+
             |      |          |          |          | 
        <----+      | [1] [11] X [2]  [3] +--+   [4] +------+
class Frippy        |          |             |              |
+-------------------+----------+-------------+--------------+--------------+
|       [12]        V          |             |              |       [12]   |
| +--\-------/   +----------+  >+----------+ | +----------+ | +--\-------/ |
| |   \----+/|   |   \-/--+ |   |   +----+ | | |   +----+ | | |   \----+/| |
| | x |\   / |   | x |0[9]|1|   | x |0   | | | | x |0   | | | | x |\   / | |
| |   +-\-/+ |   |   /-\--+ |   |   +----+ | | |   +----+ | | |   +-\-/+ | |
| |      X   |   |          |   |     [7]  | | |          | | |      X   | |
| |   +-/-\+ |   |   +----+ |   |   +-\-/+ | | |   +-\-/+ | | |   +-/-\+ | |
| | F |/   \ |   | F |null| |   | F |nuXl*-+-+>| F |nuXl| | | | F |/   \ | |
| |   /----+\|   |   +----+ |   |   +-/-\+ | | |   +*/-\+ | | |   /----+\| |
| +--/-------\   +----------+   +----------+ | +----+-----+ | +--/-------\ |
|                       [8] ^----------------+------+ ^     |              |
+--------------------------------------------+--------+-----+--------------+
                                             |        |     |
                                             |    [6] |     |
class Boingo                                 |        |     |
+--------------------------------------------+--------|-----+--------------+
|       [12]         [12]           [12]     |        |     |              |
| +--\-------/   +--\-------/   +--\-------/ +>+------|---+ +>+----------+ |
| |   \----+/|   |   \----+/|   |   \----+/|   |   +--|-+ |   |   +-\-/+ | |
| | a |\   / |   | a |\   / |   | a |\   / |   | a |nu|l| |   | a |nuXl*-+-+-+
| |   +-\-/+ |   |   +-\-/+ |   |   +-\-/+ |   |   +--|-+ |   |   +-/-\+ | | |
| |      X   |   |      X   |   |      X   |   |      |   |   |          | | |
| |   +-/-\+ |   |   +-/-\+ |   |   +-/-\+ |   |   +-\*/+ |   |   +----+ | | |
| | b |/   \ |   | b |/   \ |   | b |/   \ |   | b |nuXl| |   | b |null| | | |
| |   /----+\|   |   /----+\|   |   /----+\|   |   +-/-\+ |   |   +----+ | | |
| +--/-------\   +--/-------\   +--/-------\   +----------+   +----------+ | |
|                                                                          | |
+--------------------------------------------------------------------------+ |
                                                                             |
class String                                                                 |
+----------------------+                                                     |
|                      |                [5]                                  |
| "grok"<--------------+-----------------------------------------------------+
|                      |
+----------------------+