Code quality is not an exact science and is rather subjective, which brings the need of well defined rules and principles to follow. Clean code is all about readability, furthermore, principles like GRASP or techniques like fluent APIs makes the code even cleaner and maintainable. Design Patterns on the other hand are typical solutions to common problems in software design. You will walk away with a taste of quality principles and metrics for building quality software. Also previews of some useful books like Martin Fowler's Clean Code and Kent Beck's Implementation Patterns are presented.

1. 1Caring About Code Quality
Caring About Code
Quality
EL MAHDI BENZEKRI | elmahdi.benzekri@gmail.com
2019

2. 2Caring About Code Quality
Clean Code: A Handbook of Agile Software Craftsmanship
by Robert C. Martin
The Book

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Does it work?
What is Clean Code?
Does it scale?
Is it esthetic?
Is it maintainable?
Is it testable?
Is it short?
Is it clever?
Does it have explanatory
comments?
Is it easy to
understand?
Is it well-structured?
Is it object-oriented?

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• Focused
• Single-minded attitude
• Undistracted and unpolluted
• Readable, simple and direct
• Compact and literate
• Contains only what is necessary
• Makes it easy for other developers to enhance it
• Tests should be also clean
• Looks like it’s author cares
• FoContains no duplicates
• undations are established on tiny abstractions
What is Clean Code after all?

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• Subjective
• If you can’t measure, you can’t improve
• Identify what matters
• Defend and justify decisions.
The need for measurement

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Cyclomatic complexity
public void foo() {
if (c1) {
f1();
} else {
f2();
}
if (c2) {
f3();
} else {
f4();
}
}
• Upper bound for the number of test cases
that are necessary to achieve a complete
branch coverage
• Lower bound for the number of paths
through the control flow graph
• Desirable value: below 10
Cyclomatic complexity: 3

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Always leave the campground
cleaner than you found it.
The Boy Scout Rule

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• Came from city crime researchers
• A broken window will trigger a building into a
smashed and abandoned derelict
• So does the software
Broken Window Theory

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Composed method example
public void add(Object element) {
if (!readOnly) {
int newSize = size + 1;
if (newSize > elements.length) {
Object[] newElements = new Object[elements.length + 10];
for (int index = 0; index < size; index++) {
newElements[index] = elements[index];
elements = newElements;
}
}
elements[size++] = element;
}
}

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Implementation patterns

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Composed method example
public void add(Object element) {
if (!isReadOnly()) {
if (atCapacity()) {
grow();
}
addElement(element);
}
}

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• Instant feedback
• Allows you to make changes to code quickly
• Help you understand the design of the code you
are working on
• Writing testable code helps to achieve better
code quality
• Unit tests are a form of sample code
• Test-first forces you to plan before you code
Advantages of Unit tests

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• Whether the unit you're testing should be
isolated from its collaborators
• Mockist approach
– Isolate from dependencies
– More flexible in what you can test
• Classic approach
– No attempt to isolate unless communicating
with the collaborator is awkward
– Less brittle tests
Unit tests collaborator isolation

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• Change Risk Analysis and Prediction
• Help you identify code that might be particularly difficult to
understand, test, or maintain
• 𝐶𝑅𝐴𝑃 𝑚 = cycl_comp(m)2
∗ 1 − 𝑐𝑜𝑣𝑒𝑟𝑎𝑔𝑒
3
+ cycl_comp(m)
• A method with a CRAP score over 30 is considered
unacceptable
C.R.A.P. metric
Cyclomatic
Complexity
Coverage
required
0 – 5 0%
10 42%
15 57%
20 71%
25 80%
30 100%
31+ Not possible

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• Don’t build complex machines
• Don’t build frameworks
• Make the software so simple that there are
obviously no deficiencies
• Keep it simple, stupid (KISS)
Rube Goldberg Machines

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• Avoid Cargo cult programming
• Question authority
• Accept feedback and give feedback
Angry monkeys experiment

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DESIGN PATTERNS IN
PRACTICE
2019

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Transfer object pattern

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Front controller

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Chain of responsibility

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Proxy pattern

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• Thread safety
• Valid state
• Encapsulation
• Simpler to test
• More readable and maintainable code
Immutable Object

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Null Object

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Flyweight pattern

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Template method

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• State Pattern’s intent is to manage states of the object along with object’s behavior which changes
with its state.
• State typically involves a getStatus method and a reference back to the context
• state, behavior is autodeterminated, strategy, behavior is determinated by caller.
• Strategy Pattern is to have a family of interchangeable algorithms
• Relation between individual states/individual strategies
State vs Strategy

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Observer Pattern

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Facade Pattern

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Decorator Pattern

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THINKING
AND
CODING EFFICIENTLY

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Effective Java
• Level of access ? Minimum
• Classpath ?
• Composition vs inheritance
• Avoid side effects
• Minimize Mutability
• Check methods/constructosr parameters for validity
• Always override hashCode when you override equals
• …
• https://github.com/HugoMatilla/Effective-JAVA-Summary

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• “This” keyword
• Chained
• Popular java Fluent API’s:
– Java Object Oriented Querying (jOOQ) API
– Java 8’s Date Time API
– Java 9’s Money and Currency API
Fluent API

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• Handle UI interractions
GRASP - The Controller

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• Information expert
• Encapsulating information
GRASP - The Expert

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• Creation responsibility
• Have enough information to instantiate an object
GRASP - The Creator

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• it is a measure of how strongly related each
piece of functionality expressed by
the source code of a software module is.
GRASP - High cohesion

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• The smallest number of references
between objects as possible
• Reason of change
GRASP - Low coupling

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EMBZENZEKRI@SQLI.COM
THANK YOU FOR ATTENTION!
QUESTIONS?