Building Immutable foundations from the ground TL;DR: Pass essential attributes during object creation to reduce mutability and eliminate getters and setters. Problems Addressed Mutability
Getters
Setters
Unclear object state
Violating the least surprise principle Steps Identify essential attributes required for object creation
Create a constructor that accepts all essential attributes
Remove setter and getter methods
Update object creation calls to pass all required attributes upfront Sample Code Before public class CreditCard {
    private String cardNumber;
    private String cardHolderName;
    private String expirationMonthYear;
    private int cvv;

    public CreditCard() {} // Empty Constructor

    public void setCardNumber(String cardNumber) { 
        this.cardNumber = cardNumber; 
    }
    public void setCardHolderName(String cardHolderName) { 
        this.cardHolderName = cardHolderName; 
    }
    public void setExpirationMonthYear(String expirationMonthYear) { 
        this.expirationMonthYear = expirationMonthYear;
    }
    public void setCvv(int cvv) { 
        this.cvv = cvv; 
    }

    public String getCardNumber() { 
        return cardNumber; 
    }
    public String getCardHolderName() {
        return cardHolderName;
    }
    public String getExpirationMonthYear() {
        return expirationMonthYear; 
    }
    public int getCvv() {
        return cvv; 
    }
}

CreditCard card = new CreditCard();
card.setCardNumber("1234-5678-9012-3456");
card.setCardHolderName("Lilywhite Lilith");
card.setExpirationMonthYear("12/25");
card.setCvv(123); After public class CreditCard {
    private final String cardNumber;
    private final String cardHolderName;
    private final String expirationMonthYear;
    private final int cvv;

    public CreditCard(String cardNumber,
                      String cardHolderName,
                      String expirationMonthYear,
                      int cvv) {
        // 1. Identify essential attributes for object creation
        // 2. Create a constructor that accepts all essential attributes
        this.cardNumber = cardNumber;
        this.cardHolderName = cardHolderName;
        this.expirationMonthYear = expirationMonthYear;
        this.cvv = cvv;
    }

    // 3. Remove setter and getter methods 
    
    // Find real behavior related to credit card usage
  
}

// 4. Update object creation calls to pass all required attributes upfront
CreditCard card = new CreditCard("1234-5678-9012-3456",
                                 "Lilywhite Lilith", 
                                 "12/25", 
                                 123); Type Semi-Automatic This is a step-by-step refactor. Safety This refactoring is generally safe if you ensure you pass all essential attributes during object creation. You must update all object creation sites, which may require refactoring tools and careful review in larger codebases. Why is the code better? The refactored code enforces object integrity by requiring all essential attributes at creation time. The objects become thread-safe reducing the risk of being in an inconsistent state. AI Correction Most AI tools can correct this code with explicit instructions. You can have clear pre-prompts requesting all your code samples to favor immutability. Try Them! Remember AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Gemini

Gemini Tags Mutability Related Refactorings Refactoring 001 - Remove Setters See also https://hackernoon.com/nude-models-part-i-setters-5tm3u3y?embedable=true https://hackernoon.com/nude-models-part-ii-getters-sjo3ua2?embedable=true https://hackernoon.com/is-it-crystal-clear-for-everybody-that-a-date-should-not-mutate-wuoy3z03?embedable=true Credits Image by Denis on Pixabay This article is part of the Refactoring Series. How to Improve your Code With Easy Refactorings Building Immutable foundations from the ground Building Immutable foundations from the ground TL;DR: Pass essential attributes during object creation to reduce mutability and eliminate getters and setters. TL;DR: Pass essential attributes during object creation to reduce mutability and eliminate getters and setters. Problems Addressed Mutability Getters Setters Unclear object state Violating the least surprise principle Mutability Mutability Getters Getters Setters Setters Unclear object state Violating the least surprise principle Steps Identify essential attributes required for object creation Create a constructor that accepts all essential attributes Remove setter and getter methods Update object creation calls to pass all required attributes upfront Identify essential attributes required for object creation Create a constructor that accepts all essential attributes Remove setter and getter methods Update object creation calls to pass all required attributes upfront Sample Code Before public class CreditCard {
    private String cardNumber;
    private String cardHolderName;
    private String expirationMonthYear;
    private int cvv;

    public CreditCard() {} // Empty Constructor

    public void setCardNumber(String cardNumber) { 
        this.cardNumber = cardNumber; 
    }
    public void setCardHolderName(String cardHolderName) { 
        this.cardHolderName = cardHolderName; 
    }
    public void setExpirationMonthYear(String expirationMonthYear) { 
        this.expirationMonthYear = expirationMonthYear;
    }
    public void setCvv(int cvv) { 
        this.cvv = cvv; 
    }

    public String getCardNumber() { 
        return cardNumber; 
    }
    public String getCardHolderName() {
        return cardHolderName;
    }
    public String getExpirationMonthYear() {
        return expirationMonthYear; 
    }
    public int getCvv() {
        return cvv; 
    }
}

CreditCard card = new CreditCard();
card.setCardNumber("1234-5678-9012-3456");
card.setCardHolderName("Lilywhite Lilith");
card.setExpirationMonthYear("12/25");
card.setCvv(123); public class CreditCard {
    private String cardNumber;
    private String cardHolderName;
    private String expirationMonthYear;
    private int cvv;

    public CreditCard() {} // Empty Constructor

    public void setCardNumber(String cardNumber) { 
        this.cardNumber = cardNumber; 
    }
    public void setCardHolderName(String cardHolderName) { 
        this.cardHolderName = cardHolderName; 
    }
    public void setExpirationMonthYear(String expirationMonthYear) { 
        this.expirationMonthYear = expirationMonthYear;
    }
    public void setCvv(int cvv) { 
        this.cvv = cvv; 
    }

    public String getCardNumber() { 
        return cardNumber; 
    }
    public String getCardHolderName() {
        return cardHolderName;
    }
    public String getExpirationMonthYear() {
        return expirationMonthYear; 
    }
    public int getCvv() {
        return cvv; 
    }
}

CreditCard card = new CreditCard();
card.setCardNumber("1234-5678-9012-3456");
card.setCardHolderName("Lilywhite Lilith");
card.setExpirationMonthYear("12/25");
card.setCvv(123); After public class CreditCard {
    private final String cardNumber;
    private final String cardHolderName;
    private final String expirationMonthYear;
    private final int cvv;

    public CreditCard(String cardNumber,
                      String cardHolderName,
                      String expirationMonthYear,
                      int cvv) {
        // 1. Identify essential attributes for object creation
        // 2. Create a constructor that accepts all essential attributes
        this.cardNumber = cardNumber;
        this.cardHolderName = cardHolderName;
        this.expirationMonthYear = expirationMonthYear;
        this.cvv = cvv;
    }

    // 3. Remove setter and getter methods 
    
    // Find real behavior related to credit card usage
  
}

// 4. Update object creation calls to pass all required attributes upfront
CreditCard card = new CreditCard("1234-5678-9012-3456",
                                 "Lilywhite Lilith", 
                                 "12/25", 
                                 123); public class CreditCard {
    private final String cardNumber;
    private final String cardHolderName;
    private final String expirationMonthYear;
    private final int cvv;

    public CreditCard(String cardNumber,
                      String cardHolderName,
                      String expirationMonthYear,
                      int cvv) {
        // 1. Identify essential attributes for object creation
        // 2. Create a constructor that accepts all essential attributes
        this.cardNumber = cardNumber;
        this.cardHolderName = cardHolderName;
        this.expirationMonthYear = expirationMonthYear;
        this.cvv = cvv;
    }

    // 3. Remove setter and getter methods 
    
    // Find real behavior related to credit card usage
  
}

// 4. Update object creation calls to pass all required attributes upfront
CreditCard card = new CreditCard("1234-5678-9012-3456",
                                 "Lilywhite Lilith", 
                                 "12/25", 
                                 123); Type Semi-Automatic Semi-Automatic This is a step-by-step refactor. Safety This refactoring is generally safe if you ensure you pass all essential attributes during object creation. You must update all object creation sites, which may require refactoring tools and careful review in larger codebases. Why is the code better? The refactored code enforces object integrity by requiring all essential attributes at creation time. The objects become thread-safe reducing the risk of being in an inconsistent state. AI Correction Most AI tools can correct this code with explicit instructions. You can have clear pre-prompts requesting all your code samples to favor immutability. Try Them! Remember AI Assistants make lots of mistakes Remember AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Gemini

Gemini Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Gemini

Gemini Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini Tags Mutability Mutability Related Refactorings Refactoring 001 - Remove Setters Refactoring 001 - Remove Setters See also https://hackernoon.com/nude-models-part-i-setters-5tm3u3y?embedable=true https://hackernoon.com/nude-models-part-i-setters-5tm3u3y?embedable=true https://hackernoon.com/nude-models-part-ii-getters-sjo3ua2?embedable=true https://hackernoon.com/nude-models-part-ii-getters-sjo3ua2?embedable=true https://hackernoon.com/is-it-crystal-clear-for-everybody-that-a-date-should-not-mutate-wuoy3z03?embedable=true https://hackernoon.com/is-it-crystal-clear-for-everybody-that-a-date-should-not-mutate-wuoy3z03?embedable=true Credits Image by Denis on Pixabay Denis Pixabay This article is part of the Refactoring Series. How to Improve your Code With Easy Refactorings How to Improve your Code With Easy Refactorings

The code in this story is for educational purposes. The readers are solely responsible for whatever they build with it.

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