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Cover image for Code Smell 131 - Zero Argument Constructor
Maxi Contieri
Maxi Contieri

Posted on • Originally published at maximilianocontieri.com

Code Smell 131 - Zero Argument Constructor

Objects created without arguments are often mutable and erratic

TL;DR: Pass all your essential arguments when creating objects.

Problems

Solutions

  1. Use one complete and single constructor.

  2. Avoid Setters and Getters

Context

It is common usage using a zero-argument constructor and a bunch of setters to change it.

Beans is a well-known example of this code smell.

Sample Code

Wrong

 public Person();

// Anemic and mutable
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Right

public Person(String name, int age){
     this.name = name;
     this.age = age;
     } 
 }

// We 'pass' the essence to the object 
// So it does not mutate
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Detection

[X] Automatic

We can check all constructors, but there are some false positives.

Stateless objects are a valid example.

Tags

  • Mutability

Conclusion

Empty constructors are mutability hints and accidental implementation issues.

We need to research usages to improve our solutions.

Relations

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Credits

Photo by Ade Adebowale on Unsplash


Don't worry about design, if you listen to your code a good design will appear...Listen to the technical people. If they are complaining about the difficulty of making changes, then take such complaints seriously and give them time to fix things.

Martin Fowler


This article is part of the CodeSmell Series.

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