Java master Kaimu led three senior monks to the Hall Of
Endless Cubicles. There he gathered three novices in his
charge.
“A utility method is needed which takes an employee ID and
from it constructs a particular URL,” said Kaimu. “The logic
is not trivial, but ultimately it reduces to text
substitution.”
Kaimu gestured to the first old monk. “This one works on the
persistence tier, where all database keys are large
integers. Understandably, he wishes the method to take a
Long.”
Kaimu gestured to the second old monk. “This one works on
the business tier, which employs strong typing. He wishes
the method to take an EmployeeID object.”
Kaimu gestured to the third old monk. “This one works on the
web tier, where all data is manipulated as text. He wishes
the method to take a String.”
The master then bowed to the three monks, and bade the
novices offer their solutions.
The first novice stood. “The method should take a String,
for that representation will be most useful within the
method itself. As for the monks who prefer Long or
EmployeeID, they can easily invoke toString on those objects
and feed the result into the method.”
Said Kaimu: “When the beggar squatting in the dirt asks you
for coins, you may well demand that he lift up his bowl to
meet you. But what of the man with no elbows?”
Before the first novice could answer, the second stood. “The
apparent simplicity of invoking toString is hampered by the
caller’s need to check for null first. So the method should
take an Object, which can hold any of the three types. The
method itself can check for null, and invoke toString only
if it is safe to do so. Thus, nothing is required of the
caller.”
Said Kaimu: “Knowing the armless beggar can only accept what
is placed on his tongue, you charitably go everywhere with
rice in your pockets. Yet you toss your grains into anyone’s
mouth. How glad you make the rats and magpies!”
The third novice stood. “Three monks, three novices. Why not
three methods, each taking a different type? EmployeeID,
Long, and String. The first and second can delegate to the
third, and each can check for null.”
Said Kaimu: “Not a scrap for the rats in your village, but
how fat the beggars must be! Yet if a method takes four
parameters, will you write it eighty-one different ways? You
may waste so much time pleasing everyone that you please no
one.”
Kaimu then bade the senior monks depart, to let the novices
determine for themselves the best way to satisfy all
concerns.
The first old monk whispered as they went: “What approach
will be decided upon, do you think?”
The second old monk replied: “If they are anything like us,
it will be the one championed by the novice who shouts the
loudest.”
The third old monk nodded. “Doubtless, some of us will find
fault with the solution, yet begrudgingly we will abide by
it, and the world will continue to turn. But so it goes: we
are all of us beggars at each others’ feet.”
