Alles bleibt anders (Timeless Wisdom for Software Developers)

Alles bleibt anders   Timeless Wisdom for Software Developers Frank
Gerberding, 05.05.202

@ MilesBehind69 2 "Give someone a program, you frustrate them
for a day;   teach them how to program, you frustrate them for a lifetime." ( David Leinweber)

@ MilesBehind69 3

@ MilesBehind69 4 Muss ich ständig etwas Neues lernen?  
Muss ich ständig von Neuem lernen? 𐄂 ✓

@ MilesBehind69 5 Small is beautiful „Small is beautiful, Size
is the #1 enemy of agility; keep your systems as small as you reasonably can (but no smaller)“ ( Stefan Tilkov)

@ MilesBehind69 6 Methode aus Code-Review

@ MilesBehind69 7 Single Responsibility Principle „Do not try to
do everything. Do one thing well.“ ( Steve Jobs)

@ MilesBehind69 8 Single Responsibility Principle book flight   cancel
flight FlightService Client Code FlightRepository CancelFlight FlightRepository TimeService CustomerService MessageService book flight cancel flight store bookings find customer store   bookings get system time send messages BookFlight

@ MilesBehind69 9 Side effects can be worse than the
disease „Can placebos cause side effects? If so, are the side effects real?“ ( George Carlin)

@ MilesBehind69 10 Side effects can be worse than the
disease Component-A Client Code Component-B Component-A call result   (depends on state of A and B ) call result   (depends on   state of B ) Component-B modifies some   internal data of B modifies some   internal data of A call result   (depends only on call arguments) call result   (depends only on call arguments)

@ MilesBehind69 11 Avoid accidental complexity “Any darn fool can
make something complex; it takes a genius to make something simple.” ( Pete Seeger)

@ MilesBehind69 12 Avoid accidental complexity A Problem   Complexity
Minimum   Solution   Complexity Accidental   Solution   Complexity

@ MilesBehind69 13 Dependencies prevent flexibility „The cheapest, fastest, and
most reliable components are those that aren’t there.“ ( Gordon Bell)

@ MilesBehind69 14 Dependencies prevent flexibility depends on Component Component
Component Component Component Component Component Component Component depends on Component Component Component Component Component Component Component transitively depends on

@ MilesBehind69 15 Divide and conquer through modularization „The whole
is more than the sum of its parts.“ ( Aristoteles)

@ MilesBehind69 Base-Application 16 Divide and conquer through modularization Module-A
- Interface Module-A Module-B - Interface Module-B Module-C - Interface Module-C Plugin-A Plugin-B Plugin-C Plugin-D Plugin-E

@ MilesBehind69 17 Loose coupling prevents fire of change from
spreading „Architecture is the tension   between coupling and cohesion.“ ( Neal Ford)

@ MilesBehind69 18 Loose coupling prevents fire of change from
spreading depends on Abstraction Component-A Component-B Component-A Component-B depends on implements

@ MilesBehind69 19 The Open-Closed-Principle prepares you for the future
„A good design is not the one that correctly predicts the future, it’s one that makes adapting to the future affordable.“ ( Venkat Subramaniam)

@ MilesBehind69 20 The Open-Closed-Principle prepares you for the future
Abstraction Component Component depends on implements Component Component implements implements

@ MilesBehind69 21 Ignorance is a bliss „I know this
steak doesn't exist.   I know that when I put it in my mouth,   the Matrix is telling my brain that it is juicy and delicious.   After nine years, you know what I realize?   Ignorance is bliss.“ ( Cypher, The Matrix)

@ MilesBehind69 What ( Visible) 22 Ignorance is a bliss
How   ( Hidden) Client   Code

@ MilesBehind69 23 Avoid unnecessary work „Remember that there is
no code faster   than no code.“ ( Taligent’s Guide to Designing Programs)

@ MilesBehind69 24 Avoid unnecessary work persons.filter {"a" in it.lastName
} .map {"${it.firstName} ${it.lastName}" } .filter {it.length > 15 } .take(5) persons.stream( ) .filter {"a" in it.lastName } .map {"${it.firstName} ${it.lastName}" } .filter {it.length > 15 } .limit(5 ) .collect(Collectors.toList()) persons.asSequence( ) .filter {"a" in it.lastName } .map {"${it.firstName} ${it.lastName}" } .filter {it.length > 15 } .take(5 ) .toList() Evaluation Duration 0 ms 20 ms 40 ms 60 ms Person Count 100 10.000 1.000.000 Kotlin List Kotlin Sequence/Java Stream Kotlin   Lists Kotlin   Sequences Java   Streams

@ MilesBehind69 25 I/O is slow „Nothing travels faster than
the speed of light with the possible exception of bad news.“ ( Douglas Adams)

@ MilesBehind69 26 I/O is slow 1 MByte/sec 100 MByte/sec
10.000 MByte/sec 2000 2010 2020 Storage Network Memory 50 ⨉ 400 ⨉

@ MilesBehind69 27 Quality leads to productivity „The paradox is
that when you focus on productivity, long- term improvements are rarely made.   On the other hand, when you focus on quality, productivity improves continuously.“ ( John Seddon)

@ MilesBehind69 Aufwand pro Feature Zeit Kein Fokus auf Qualität/Tests
Fokus auf Qualität/Tests 28 Quality leads to productivity Mehraufwand mit Fokus auf Qualität Mehraufwand ohne Fokus   auf Qualität Produktivität

@ MilesBehind69 29 Immutability is your code’s armor „One of
the most difficult elements of program design   is reasoning about the possible states of complex objects. Reasoning about the state of immutable objects,   on the other hand, is trivial.“ ( Brian Goetz)

@ MilesBehind69 30 Immutability is your code’s armor ImmutableItem ImmutableItem
MutableItem modify modify = copy ImmutableCollection ImmutableCollection modify = create changes reference previous version

@ MilesBehind69 31 Improving testability improves design „Always code as
if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.“ ( John F. Woods)

@ MilesBehind69 32 Improving testability improves design Loose Coupling Immutability
Keep things small Open-Closed- Principle Avoid Dependencies Single Responsibility Principle Quality is   Productivity Make things   easily testable Avoid side effects

@ MilesBehind69 33 Good names improve readability „There are 2
hard problems in computer science:   cache invalidation,   naming things,   and off-by-1 errors.“ ( Leon Bambrick)

@ MilesBehind69 34 Documentation is a love letter to your
future self „A person who won't read   has no advantage over one who can't read.“ ( Mark Twain)

@ MilesBehind69 35 Modularization Loose Coupling Immutability Keep things small
Open-Closed- Principle I/O is slow Lazy Evaluation Avoid Dependencies Quality is   Productivity Make things   easily testable Name things well Documentation Avoid accidental   complexity Avoid side effects Information Hiding Single Responsibility Principle

@ MilesBehind69 36 „One of the best programming skills you
can have   is knowing when to walk away for awhile.“ ( Oscar Godson)

Vielen Dank für   Eure Aufmerksamkeit! https://speakerdeck.com/milesbehind69   http://frank.gerberding.blog https://twitter.com/milesbehin69
Zeichnungen von Sandra & Frank Gerberding

Alles bleibt anders (Timeless Wisdom for Software Developers)

Alles bleibt anders (Timeless Wisdom for Software Developers)

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