How to eliminate If-Statements and InstanceOf with the Visitor-Pattern

Using the visitor pattern to eliminate If-Statements and InstanceOf


We all know the visitor pattern from the book GoF (gang of four) or from other famous books. The examples in there are usually associated with trees or composite structures. I was always searching for real life examples, where this pattern could be used, making software reusable and more readable. During a refactoring task, a collegue of mine had a really good idea, that i want to share with you.


Here is the code fragment from the method we want to refactore. The method has a lot of if-statements and instanceOf in there. It maps contacts to data transfer objects (DTO)

public static void mapKontakte(ContactType contactType, List<ErweiterteKontakt<? extends StringDomainEnum>> kontakte) {
        ch.abraxas.tax.register.registerimport.parser.ech0046.v10.ObjectFactory ech0046Factory =
                new ch.abraxas.tax.register.registerimport.parser.ech0046.v10.ObjectFactory();
        for (ErweiterteKontakt<? extends StringDomainEnum> kontakt : kontakte) {
            if (kontakt instanceof Telefon) {
                PhoneType phoneType = ech0046Factory.createPhoneType();
                phoneType.setPhoneCategory(new BigInteger( ((Telefon) kontakt).getKategorie().key()));
                phoneType.setPhoneNumber(kontakt.getDetail());
                contactType.getPhone().add(phoneType);
            } else if (kontakt instanceof Email) {
                EmailType emailType = ech0046Factory.createEmailType();
                emailType.setEmailCategory(new BigInteger( ((Email) kontakt).getKategorie().key()));
                emailType.setEmailAddress(kontakt.getDetail());
                contactType.getEmail().add(emailType);
            } else if (kontakt instanceof Internet) {
                InternetType internetType = ech0046Factory.createInternetType();
                internetType.setInternetCategory(new BigInteger( ((Internet) kontakt).getKategorie().key()));
                internetType.setInternetAddress(kontakt.getDetail());
                contactType.getInternet().add(internetType);
            }
            // Should we use an else branch to verify that we are mapping all Kontakte?
        }
    }

here is the same method after refactoring:

public static void mapKontakte(ContactType contactType,
   List<ErweiterteKontakt<? extends StringDomainEnum>> kontakte) {

  ErweiterterKontaktVisitor visitor = new BindingObjectFromKontaktVisitor(contactType);
  for (ErweiterteKontakt<? extends StringDomainEnum> kontakt : kontakte) {
   // calls the Kontakt to use the visitor
   kontakt.accept(visitor);
  }
 }

Well here is how to do it. In the abstract class ErweiterteKontakt we define following method:

public abstract void accept(ErweiterterKontaktVisitor visitor);

Then we implement this abstract method in the classes Email, Telefon and Internet. They all extends ErweiterkeKontakt.

 @Override
 public void accept(ErweiterterKontaktVisitor visitor) {
  visitor.visit(this);
 }

Defining the visitor interface

public interface ErweiterterKontaktVisitor {

 /**
  * Visit the telefon
  * 
  * @param telefon
  */
 public void visit(Telefon telefon);

 /**
  * visit the email
  * 
  * @param email
  */
 public void visit(Email email);

 /**
  * visit the internet
  * 
  * @param internet
  */
 public void visit(Internet internet);
}

Then Implementing the Visitor itself:

public class BindingObjectFromKontaktVisitor implements ErweiterterKontaktVisitor {

 private ch.abraxas.tax.register.registerimport.parser.ech0046.v10.ObjectFactory ech0046Factory = new ch.abraxas.tax.register.registerimport.parser.ech0046.v10.ObjectFactory();

 private ContactType contactType;

 /**
  * Konstruktor
  */
 public BindingObjectFromKontaktVisitor(ContactType contactType) {
  this.contactType = contactType;
 }

 /**
  * {@inheritDoc}
  */
 @Override
 public void visit(Telefon telefon) {
  PhoneType phoneType = ech0046Factory.createPhoneType();
  phoneType.setPhoneCategory(new BigInteger(telefon.getKategorie().key()));
  phoneType.setPhoneNumber(telefon.getDetail());
  contactType.getPhone().add(phoneType);
 }

 /**
  * {@inheritDoc}
  */
 @Override
 public void visit(Email email) {
  EmailType emailType = ech0046Factory.createEmailType();
  emailType.setEmailCategory(new BigInteger(email.getKategorie().key()));
  emailType.setEmailAddress(email.getDetail());
  contactType.getEmail().add(emailType);

 }

 /**
  * {@inheritDoc}
  */
 @Override
 public void visit(Internet internet) {
  InternetType internetType = ech0046Factory.createInternetType();
  internetType.setInternetCategory(new BigInteger((internet).getKategorie().key()));
  internetType.setInternetAddress(internet.getDetail());
  contactType.getInternet().add(internetType);

 }
}

Done!
No more If-Statements, no more InstanceOf and the code is now extandable and more flexible.

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When do we need DataTransferObjects - DTOs (indicators)

Indicators for DTOs (Data Transfer Objects)


DTO should be used with care. Generally we decide case by case, whether we shall introduce DTO layers which generates more complexity, or whether we work directly with the domain objects (DOs). The list below will assist us by our decission.


When can i use DomainObjects(DOs) direct to visualize details in the GUI?


Case 1: 
you can do it (and shall do it) by readonly views and if the domain object doesn't need to go back to the database. During this process the client may change values of the domain object if necessary. The only condition: The domain object is not returned to the database.


Case 2: 
If other software parts use the same service needing the whole content of a domain object. In this case you may get and use the whole domain object. But if you wanna change some values of it and store it back into the database, then you'll need new objects called: prefixDTOData. why that? Because otherwise we would force the service which writes the attributes into database to iterate over the whole domain object looking and comparing for changes before writing down in the database. 


When shall i better use DTOs? 


Case 1:
Use DTO's if the domain object is huge, but you just need a few attributes of it! For large domain objects, in which the client visualize, change or display only a few of its attributes. In this case we recommend to use the notation: prefixDTO. This is the object which the client uses to do its works. The service gets the Domain Object, creates the DTO and gives it back. If this DTO is used in a wizard or kind of formular in which the user may type something in setting values, which means that you have to store the typed information into database, then you should use in addtion to the DTOs new objects called: prefixDTOData. why that? Because otherwise we would force the service which writes the attributes into database to iterate over the whole domain object (remember that the domain object is huge) looking and comparing for changes before writing down in the database.


Case 2:
Use DTOs if the client has to show fields from different domain objects. In this special case you may consider putting all the needed attributes together already in the database creating the DTO in the server which is passed to the service going to the client. The client creates analoque to Case 1 a prefixDTOData an gives it back to the service. the reasons are the same as in explained in Case 1.


What are the disadvantages of DTOs?

You have/create additional complexities, which means that if things has to be changed, you have to make the changes everywhere in your code.

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How to use the "Builder Pattern" in factories?

Using the "Builder Pattern" in Factories making your classes testable

Hi there! In this blog i want show to you how we can combine the builder pattern with the factory pattern making our classes testable. 

Common Problem

In many cases we have (must) separate Domain Objects (DOs) from the objects we use to visualize something in der GUI. For this reason we create in most of the cases Domain Transfer Objects (DTO's) which hold the values from the DO's in it. With a DTO Factory we would be able to create and fill up all attributes of it with default values. This is a good practise because this way we can use the factory to create DTO's also while testing it. That's when the builder pattern comes in. Combining the builder pattern with the factory pattern allow us to create default DTO's as well specific DTO's. Important: If you don't know when the usage of DTO's is appropriate, then you may read this post first: "When do we use DTO's"


UML of the example:

Example Address

Let's say we have the domain object (class) called Address that looks like this:

// Domain Object
public class Address {

    // only a few attributes to show the idea behind it
    private String street;
    private String land;

    public String getStreet() {
        return this.street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getLand() {
        return this.land;
    }

    public void setLand(String land) {
        this.land = land;
    }

}

The DTO could look like this:

public class AddressDTO {

    private Address address;

    public AddressDTO() {
        this.address = new Address();
    }

    public Address getAddress() {
        return this.address;
    }

    public void setAddressDTO(Address address) {
        this.address = address;
    }
}

Then we would also need a mapper. It could look like this:

public class AddressMapper {

    Address domainAddress;
    AddressDTO addressDTO;

    public AddressMapper(Address domainAddress, AddressDTO addressDTO) {
        this.domainAddress = domainAddress;
        this.addressDTO = addressDTO;
    }

    public AddressDTO mapDomainToDto() {
        this.addressDTO.getAddress().setLand(this.domainAddress.getLand());
        this.addressDTO.getAddress().setStreet(this.domainAddress.getStreet());
        return this.addressDTO;
    }

    public Address mapDtoToDomain() {
        this.domainAddress.setLand(this.addressDTO.getAddress().getLand());
        this.domainAddress.setStreet(this.addressDTO.getAddress().getStreet());
        return this.domainAddress;
    }
}

The factory could be implemented like this:

public class AddressDTOFactory {

    private AddressDTO addressDTO;
    private boolean instanceObserver;
    private static AddressDTOFactory factory;

    // factory pattern knows how to create the DTO
    private AddressDTOFactory() {
        super();
        this.instanceObserver = true;
        this.addressDTO = create();
    }

    // singleton pattern instantiates the factory
    public static AddressDTOFactory getInstance() {
        return (factory == null) ? (factory = new AddressDTOFactory()) : factory;
    }

    // public mock values for testing purposes
    public static String DEFAULT_STREET = "MyStreet";
    public static String DEFAULT_LAND = "USA";

    // builder pattern can be used to mock tests
    public AddressDTOFactory street(String street) {
        createNewObjectIfNotObserved();
        this.addressDTO.getAddress().setStreet(street);
        return factory;
    }

    public AddressDTOFactory land(String land) {
        createNewObjectIfNotObserved();
        this.addressDTO.getAddress().setLand(land);
        return factory;
    }

    public AddressDTOFactory defaultFilling() {
        createNewObjectIfNotObserved();
        this.addressDTO.getAddress().setLand(DEFAULT_LAND);
        this.addressDTO.getAddress().setStreet(DEFAULT_STREET);
        return factory;
    }

    public AddressDTOFactory fillMandatoryFields() {
        createNewObjectIfNotObserved();
        // let's assume that land is a mandatory field in GUI and database
        this.addressDTO.getAddress().setLand(DEFAULT_LAND);
        return factory;
    }

    public AddressDTO getObject() {
        if (this.instanceObserver) {
            this.instanceObserver = false;
        } else {
            this.addressDTO = create();
        }
        return this.addressDTO;
    }

    // ensure right instance
    private void createNewObjectIfNotObserved() {
        if (!this.instanceObserver) {
            this.instanceObserver = true;
            this.addressDTO = create();
        }
    }

    private AddressDTO create() {
        return new AddressMapper(new Address(), new AddressDTO()).mapDomainToDto();
    }

}  

Now we have a testable AddressDTO with deterministic character that can be reused for several tests according to your needs. The test could look like this:

import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;

public class AddressDTOFactoryTest {

    AddressDTO defaultAddressDTO;
    AddressDTO mandatoryAddressDTO;
    AddressDTO emptyAddressDTO;
    AddressDTO customizedAddressDTO;
    AddressDTO totallyEmptyAddressDTO;

    public AddressDTOFactoryTest() {
        super();
    }

    @Before
    public void setUp() throws Exception {
        AddressDTOFactory factory = AddressDTOFactory.getInstance();
        this.defaultAddressDTO = factory.defaultFilling().getObject();
        this.mandatoryAddressDTO = factory.fillMandatoryFields().getObject();
        this.emptyAddressDTO = factory.getObject();
        this.customizedAddressDTO = factory.street("Av. Copacabana").land("Brazil").getObject();
        this.totallyEmptyAddressDTO = factory.getObject();
    }

    @Test
    public void testDefaultAddressDTO() {
        Assert.assertEquals(AddressDTOFactory.DEFAULT_LAND, this.defaultAddressDTO.getAddress().getLand());
        Assert.assertEquals(AddressDTOFactory.DEFAULT_STREET, this.defaultAddressDTO.getAddress().getStreet());
    }

    @Test
    public void testMandatoryAddressDTO() {
        String empty = null;
        Assert.assertEquals(AddressDTOFactory.DEFAULT_LAND, this.mandatoryAddressDTO.getAddress().getLand());
        Assert.assertEquals(empty, this.mandatoryAddressDTO.getAddress().getStreet());
    }

    @Test
    public void testEmptyAddressDTO() {
        String empty = null;
        Assert.assertEquals(empty, this.emptyAddressDTO.getAddress().getLand());
        Assert.assertEquals(empty, this.emptyAddressDTO.getAddress().getStreet());
    }

    @Test
    public void testCustomizedAddressDTO() {
        Assert.assertEquals("Brazil", this.customizedAddressDTO.getAddress().getLand());
        Assert.assertEquals("Av. Copacabana", this.customizedAddressDTO.getAddress().getStreet());
    }

    @Test
    public void testTotallyEmptyAddressDTO() {
        String empty = null;
        Assert.assertEquals(empty, this.totallyEmptyAddressDTO.getAddress().getLand());
        Assert.assertEquals(empty, this.totallyEmptyAddressDTO.getAddress().getStreet());
    }

}

Conclusion

A simple re-adjust or a little more class design can save you a lot of unnecessary, duplicated code and time. It makes the maintenance easier. Think always about how to test it while writing new classes. JUnit tests can be written faster and more consistent. This simple example is a very simplified class. In the real life an Address class is much bigger with a lot more attributes used inside. 

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Whats your code style? isBigger contest!

Whats your code style? isBigger(...) contest!

Rules

Hi there! In this blog i want to see and learn from you. Post a), b), c) and so to show us how you code and why. Share your expirience with us. You may type/post your own solution if it isn't here. The goal of this post is to figure out the best code snippet to solve a specific, concrete problem as clean as you can and to share it with the world. 

The Task

Tell us how you would resolve spontaneously following current task:
how would you write a method that checks if one value is greater than the other? 

Solution A)

boolean isBigger( int a, int b){ 
 boolean result=false;
 if(a>b){
  result=true;
}
return result;
}

Solution B)

boolean isBigger( int a, int b){ 
 if(a>b){
  return true;
}
return false;
}

Solution C)

boolean isBigger( int a, int b){ 
 return a>b? true: false;
}

Solution D)

boolean isBigger( int a, int b){ 
 return a>b;
}

Solution E)

boolean isBigger( int a, int b){ 
 return Integer.valueOf(a).compareTo(Integer.valueOf(b)) <0;
}

Solution F)

interface compare<T>{
 boolean isBigger(T a, T b);
}

Solution G)

<T> boolean isBigger( T a, T b){ 
 return a > b;
}

Solution H)

boolean isLeftValueBiggerThanRightValue ( int leftValue, int rightValue){ 
  return leftValue > rightValue && leftValue != rightValue;
}

Solution I)

<T> boolean isBigger( T value1, T value2){ 
 final int equal = 0;
 return T.valueOf(value1).compareTo(T.valueOf(value2)) > equal;
}

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Clean code theory in English

Clean code theory in English

Table of contents

Clean Code Theory

What do the colors mean ?

When do i change from one color to another ?

What does red, orange, yellow, green and blue mean ?

How can i motivate other developers ?

How could we improve the quality of this article ?

Source code convention tools

Literature, good books and references

How can i subscribe/feed this blog ?

Want to stay up to date ?

How can i rate this blog ?

Where do i find more clean code knowledge and gadgets?

Clean Code Theory

Hi there! Inspired by the geman website www.clean-code-developer.de i have lauched the treslines.com initiative with the aim to make it also popular to the english speakers. In this blog i wanna make you familiar with the basic colors of the clean code initiative and its meaning.

What do the colors mean ?

Well, In the initiative there are 7 rotational degrees. It starts from black, thru red, orange, yellow, green, blue till white. Black means only that you are interested in learn more about it and are preparing yourself to get started. Personally, i do not thing that we nescessarily need this degree. It says only that you are interested in it. www.treslines.com offers gadgets to support the iniciative. There you’ll never find the colors black and white. The white degree means that the developer are working with a huge openminded horizont. Instead of wearing the white degree, the developer should turn back to the first degree and start it from the beginning again. Thats the reason we say ratational degrees.

When do i change from one color to another ?

Well, thats up to you. I recommend a period of 1-2 month each degree.

What does red, orange, yellow, green and blue mean ?

These are interesting degrees. In it we will find always design principles to apply and best practises to use. Check www.treslines.com for gadgets and know how about clean code as well agile development.

 

Principles

1. Don't Repeat Yourself (DRY)

2. Keep It Simple, Stupid (KISS)

3. Favor Composition over Inheritance (FCoI)

4. Beware of Optimisations (BoO)

Practises

1. Scouts rules

2. Root Cause Analysis

3. Version Control

4. Simple Refactoring

5. Daily Reflection of your Work

 

Principles

1. Single Level of Abstraction (SLA)

2. Single Responsability Principle (SRP)

3. Separation of Concerns (SoC)

4. Source Code Conventions

Practises

1. Issue Tracking

2. Auto Integration Tests

3. Read, read, read

4. Reviews

  

Principles

1. Interface Segregation Principle (ISP)

2. Dependency Invertion Principle (DIP)

3. Liskov Substitution Principle (LSP)

4. Principle of Least Astonishment (PoLA)

5. Information Hiding Principle (IHP)

Practises

1. Auto Unit Tests

2. Mockups

3. Code Coverage Analyse

4. Participation in professional events

5. Complex Refactoring

Principles

1. Open Close Principle (OCP)

2. Tell don't ask

3. Law of Demeter (LoD)

Practises

1. Continuous Integration I

2. Static Code Analysis

3. Inversion of Control Container

4. Expirience  sharing

5. Measure of Errors

Principles

1. Design & Implementation do not overlap (no inconsistency)

2. Implementation reflects design

3. You Ain't Gonna Need It (YAGNI)

Practises

1. Continuous Integration II

2. Iterative development

3. Component orientation (package structure)

4. Test First

How can i motivate other developers ?

Well i do that by talking about, i wear my treslines.com t-shirt, i wear my bracelets with the CCD (Clean Code Developer Initials and colors) and i use my brand new treslines bag. It feels fantastic and even on the train people start talking to me asking about it. It is also a great idea to motivate agile teams and to share your expirience. You may want a great gift to show your appreciation to your team. Surprise them with a gadget from www.treslines.com. I love it.

   

Other interesting blogs

·         How can i indicate the quality of my clean code to other developers?

·         How can i avoid violation of the DRY principle? (Don't Repeat Yourself)

·         How to write good, reusable comments without repeating yourself? (DRY)

·         How to wirte less comments without loosing context in your app?

·         Why do you need source conventions in your company?

·         How to write valueable documentation in your company?

·         What are the contraindications for agile projects? (checklist)

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Write cleaner code and stand out!

Clean Code - A Handbook of Agile Software Craftsmanship: https://amzn.to/33RvaSv

This book is very practical, straightforward and to the point! Worth every penny!

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What are the contraindications for agile projects?

Table of contents

What are the contraindications for agile projects? (checklist)

When are agile methods suitable ?

How could we improve the quality of this article ?

Source code convention tools

Literature, good books and references

How can i subscribe/feed this blog ?

Want to stay up to date ?

How can i rate this blog ?

Where do i find more clean code knowledge and gadgets?

What are the contraindications for agile projects? (checklist)

When are agile methods suitable ?

Agiler Background: The agile approach is not always the best solution. There are work environment or circumstances that militate against the agile approach. Below are the contra-indicators to observe and evaluate:. Agile Contraindicators: These are the criteria, which does not speak for the agile approach. In this case, other approaches shall be favored.                 Contraindications Customer o  The project goal is not SMART. The goal is not clear. (specific, measurable, appropriate, relevant, terminated) o  process is defined and regulated. (e.g. by Authority or Law) o  Nice-To-Have-projects. If the pressure required is missing or it has no great significance for the organization. (No pressure = no result value) o  Customer’s decision takes a long time. When agile process, the feedback is an important element. The absence of this element, makes the project to fail. o  Lengthy change request process. These are formalized change process. The project stays still. o  No user or customer contact. Projects without user or costumer contact are difficult to perform agile. o  customer does not control the outputs. The customer must take care of the project. At least 50% of the time available shall be invested, otherwise the above-mentioned problems will arrive. o  creation of life critical software. If the meaning of provability is higher than the agile approach. o  fear of responsibility. If errors are not seen as an opportunity to learn, but interpreted as misconduct charge. o  Client does not support the agile approach. To customer needs to come and play its role in the feedback activity. o  No work on site possible. For agile methods is the close cooperation with customers and users very important. o  fixed price projects - in such cases, consider whether or not feature driven development would be appropriate. It comes from fixed-price combinations. o  Client is an authority - If the Customer is an authority, most of the decision paths takes to long, fixed price, a given process, i.e. a collection of some contraindications. Contraindications Developers o  No experience with agile projects, and no coach available. o  unwillingness or inability to learn. Agile software development is a learning process. o  culture of command and obedience - in a strictly hierarchical culture that grants the instructions almost like commands, each devbeloper is controlled so that any error is found for a guilty person, are not suitable for the application of agile methods. o  If developers do not want user contact - then it is hardly possible to apply agile methods. o  High developer fluctuation which is not good for the team o  Developer does not accept to work on site if needed or possible. o  No management commitment to an agile method - without it is not possible. Contraindication Technology o  Long build time Agile Tip! Book tip: Agile software development, values, concepts, methods of Wolf-Gideon Bleek - Henning Wolf-Morgan Kaufmann Publishers, - ISBN: 978-3-89864-473-0

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Why do you need a valuable system documentation?

Why do you need a valuable system documentation ?

Table of contents

How to write valuable system documentation with agile principles ?

How can i figure out if my documentation is valuable ?

How does the structure of a good documentation looks like?

Why do you need the system-documentation in this sequence?

How can i optimize my system documentation?

Don’t i need process documentation?

How can i avoid redundant documentation?

How could we improve the quality of this article ?

Source code convention tools

Literature, good books and references

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Want to stay up to date ?

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How to write valuable system documentation with agile principles ?

Hi there! In this blog i wanna show you, why agile concepts need a valueable documentation and why to many developers missunderstand the agile manifest. You’ll see and understand how to structure the documentation, to figure out a good, valuable documentation saving a lot of time. This blog will give you some tequiniques and methods and best practices making your company more profittable as you always has dreamed of it. Share this expirience with other developers.

How can i figure out if my documentation is valuable ?

Well, to understand that, we must find out what is essencial needed and why! To do so before writting any documentation ask yourself those valuable questions:

Document purpose : Why do i really need this documentation ?

Documentation sort : How does the minimally systematic looks like ?

If you can’t aswer those questions, do not spend a lot of time writing something that nobody will read. We only write documentation if it brings an additional benefit.

Important: If it is possible to solve or clear something over conversation, favor this way over writing documentation.

How does the structure of a good documentation looks like?

Well first of all we must know, what kind of documentation a software really needs and how to differentiate between system-documentation and stakeholder-documentation.

A system-documentation looks normally like this acc. to the best practises :

·         Architecture overview (maintenance, build deployement, development)

·         Interface handbook (for external partners)

·         Operating handbook (for operation, installation etc.)

·         Admin handbook (for context administration)

·         Support handbook (after delivery and only if needed)

This was a template. To be sure you have covered the needs of your stakeholders show it to them and ask for feedbaks. It is always better to make pro-active a proposal because otherwise the stakeholders could say: i need it all or everything is nescessary.

Why do you need the system-documentation in this sequence?

Well thats a good and very important question, because here you get the reasons why it tis essencial to have it.

We can expect that the maintenance and support/service phase is avarage 3 times bigger than the construction phase. In agile contexts even much bigger because of the short delivery cycles. The system-documentation you need exactly for this phase. (For the life cycle after delivery). For this reason the system-documentation must document mainly all information you need to maintain and support the system without asking developers or getting know-how from experts, that may no longer work in the company.

Construction vs Maintenance (3-5 times bigger)

|__________|__________|__________|__________|__________|__________|

How can i optimize my system documentation?

Well the principle here is not what ist possible, but what is really nescessary. Project-documentation is not a system-documentation. Favor the direct conversation with the stakeholders and ask them what they really need and why. The system-documentation contains in most of the cases all information needed.

The only reasons to write project documentation are :

·         Big projects : If the direct project communication is not possible.

·         High risk : to control risks. Usually medical projects and projects for the state.

·         Law requirements : the law requires it.

Don’t i need process documentation?

Good question. Sure! Process documentation is an internal and structural documentation. The most companies has it already, since they are ISO-Certified. This kind of documentation defines rules, process, concepts, models, project plan, meetings etc. If your company does not have an established process documentation you should do ti now ! Don’t think you can live without it. This is only true if your company has 3-5 employees.

How can i avoid redundant documentation?

Example : You do not have to write additional documentation if the information is normally only available for developers. Cookbooks, Source code, JavaDoc etc. describe and help developers enough. Do not spend time, documenting those things. Developers will do it automatically, if they need. Instead you should insist on a cookbook by developers. (developers should do that at a minimum to ensure know-how-transfer)

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Be sure to read, it will change your life!

Show your work by Austin Kleon: https://amzn.to/34NVmwx

This book is a must read - it will put you in another level! (Expert)

Agile Software Development, Principles, Patterns, and Practices: https://amzn.to/30WQSm2

Write cleaner code and stand out!

Clean Code - A Handbook of Agile Software Craftsmanship: https://amzn.to/33RvaSv

This book is very practical, straightforward and to the point! Worth every penny!

Kotlin for Android App Development (Developer's Library): https://amzn.to/33VZ6gp

Needless to say, these are top right?

Apple AirPods Pro: https://amzn.to/2GOICxy

😱👆 PROMOTIONAL DISCOUNT: BOOKS AND IPODS PRO 😱👆