Separate steps
Split the algorithms into separate steps that can be done one by one.
Design the intermediate data to be created by the steps and used by the next ones.
Create sequences of steps. That is the easiest to be understood by the human mind.
Separate features
Separate features
Implement different features and use cases in different parts of the code.
Avoid common code above different features.
Avoid implementing use cases with a common code and then branching them from there.
Never join use cases again, once they are separated.
Separate data and procedures
For data processing always design the data first.
Model the business results with the data. That's why it is called a 'data model'.
Create separate data loaders/collectors and data processors.
In Java implement equals(), hashcode() and toString() of data classes.
It will help the testing and debugging.
Avoid using Maps in data models. They will make the data 'unfinished'.
Create code units with
a well-defined and immutable (or effectively immutable) input data model,
and a well-defined and immutable (or effectively immutable) output data model.
Avoid additional data collection during data processing.
Test code units with input/output data.
Simply test their equality.
Separate method types
Dispatcher method
Redirecting method outputs to method inputs.
Implementation method
Usually returns a result.
Strive to create only these two method types.
Break long methods into multiple methods until you reach it.
Separate constants
Don't collect constants at the top of the class.
Put constants in the class that is responsible for it by business logic.
Collect constant value sets into enums.
Separate business code and technical code
Hide technical details behind business logic.
Don't pollute business functionality with technical details or the other way around.
Don't mix technical implementations with business logic implementations.
Don't extend generic technical classes (e.g., Collections) to create a business-specific implementation.
Always name variables after their business meaning.
E.g., don't call a map 'map' a result 'result' etc.
Organize code by SRP
Every part of the code should implement only one part of the business logic. (The original SRP.)
Every part of the business logic should be implemented by one part of the code.
A 'part' of the code can be any level, like a method, class, package, module, etc.
Apply high cohesion
Put together what belongs together.
Methods or classes that call each other.
Method and class implementation are simply code blocks that hold elements together.
Create inner classes to group a few methods within a larger class.
A package is also a bracket that holds classes together
Minimize the interface to a group of procedural codes.
One public method for one class.
One public class for one package.
Treat classes as code units
Consider maintenance costs when choosing a solutions.
Directly call subroutines
No internal ad hoc frameworks
No pets - they will become monsters
No fancy solutions
No tricky solutions
Quit OOP
Don't use inheritance. Overriding is forbidden.
Use composition.
Use classes to simply organize code into components.
Use your programming language as a structured language.
Write procedures and call them directly.
No frameworks over frameworks
Use them as it is
Avoid design patterns
No Builder
No visitor
Use complex solutions only if really necessary
Design and document them.
Avoid indirection
Preference
No indirection
Interface
Lambda
Subclass
Avoid passing lambdas to methods
Minimize to 'attributes'
Avoid call-back classes
Avoid child classes
Don't pass Maps as parameters
Use them where you create them
Don't use Maps in data models
Minimize callbacks
Callbacks are code injection
Callbacks are branching
Callbacks are parallels
Callbacks are "frameworks"
Image with callback: parallels
Separate use cases
As early as possible
In data models
Never join separated use cases
Organize ifs properly
Use guardian pattern
Decrease indentation
Don't indent the main payload of the method
Consider the cyclomatic complexity of an entire implementation of a feature or use case, not only of one method.
Create sequences
Image with sequences
Image with callback
Image with common code
Image with branching
Branchings are parallels
Write common code that is really common
Put related static information into enums.
Once you have the enums, you can get the related information without branching.
Don't use it to reach procedural code. I.e. don't use it for functions, lambdas, method references. They need a different solution.
Decrease dependencies
Make everything final / immutable
or effectively final / immutable
Data should be final / immutable
Avoid side effect programming
Mutables cannot be used as keys.
Classes should be final
But because of the mocking framework they cannot be
Investigate #xx
Organize code by SRP
Treat classes as code units
closed
finished / final
tested
minimize interfaces
Access the one functionality through one way (one method)
high cohesion
low coupling
everything should do only one thing
method
class
package
module
Don't increase visibility
Minimize interfaces
Access the one functionality through one way (one method)
Fully understand the business requirement before coding
Don't start with the coding.
Put aside your programming language.
Put aside your implementation ideas.
Don't code until you don't understand the specification perfectly.
Don't skip the design.
Create examples if necessary.
Create graphs or UML-s if necessary.
Refine the specification into code
Refine the specification into a pseudo-code.
This is a language-independent implementation of the business logic.
This is the actual program programmers should write!
Implement the pseudo-code in your programming language.
Names in the program should be the same as in the pseudo-code.
Implement the steps of the pseudo-code in the real code.
E.g., the call hierarchy of the methods should be the pseudo-code.
Chose the most simple and straightforward implementation.
Usually, this consists only of simple method calls.
The methods are simply grouped into components (procedural classes).
Organize code by business logic
Implement one feature under one package or module.
Name components and variables by their business meaning.
Name them by actions, functions, use cases, etc.
Reading the names in the code should show the business logic.
Always provide business code with names
Extract implementations of the business logic into methods and components with proper names.
Don't inline business implementation into other code.
Implement one business functionality only once.
Avoid code repetition.
Separate business code and technical code
