Code Smell 144 - Fungible Objects

We have heard a lot about NFTs. Now we master the Fungible concept

TL;DR: Respect the MAPPER. Make fungible what is Fungible in real-world and vice-versa.



  1. Identify fungible elements on your domains

  2. Model them as interchangeable


According to Wikipedia

Fungibility is the property of a good or a commodity whose individual units are essentially interchangeable and each of whose parts is indistinguishable from another part.

In software, we can replace fungible objects with others.

When mapping our objects with real ones, we sometimes forget about the partial model and build over design.


Sample Code


public class Person implements Serializable {
    private final String firstName;
    private final String lastName;

    public Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;

shoppingQueueSystem.queue(new Person('John', 'Doe'));


public class Person  { 

shoppingQueueSystem.queue(new Person());
// The identity is irrelevant for queue simulation


[X] Manual

This is a semantic smell.

We need to understand the model to check whether it is right or not.


  • Over Design


Make fungible what is fungible and vice-versa.

Sounds easy but requires design skills and avoiding accidental complexity.


Photo by Andrey Metelev on Unsplash

People think that computer science is the art of geniuses but the actual reality is the opposite, just many people doing things that build on each other, like a wall of mini stones.

Donald Knuth

This article is part of the CodeSmell Series.