Home / Questions / 7476
Accepted
Jordi Castilla
Asked: 2020-04-12 03:14:55 +0800 CST 2020-04-12 03:14:55 +0800 CST

Contraindications of static import?

  • 772

I am analyzing a code and I have found the class Constantes, which, as its name indicates, has this structure:

public final class Constantes {
    public static final String PREFIJO = "prefijo_";
}

In another class I have seen this import:

import static mi.paquete.Constantes.*;

So when using the constant class attributes you do so directly by name,

String nombreFichero = PREFIJO + nombre;

No need to reference the class as with normal imports:

String nombreFichero = Constantes.PREFIJO + nombre;

I did not know the technique of import staticand it seems quite interesting to me to clean code, as long as:

  • Your application is well structured
  • used with head
  • Don't create confusion by knowing where the constants come from.

But:

  • Are there any contraindications when using this technique?
java

2 Answers

  1. Best Answer

    This feature is available since Java 6 and supports a lot of code reduction and readability. Just be careful in case you statically import two or more classes that have static elements (field or method) with the same name since the compiler will not know which class to choose and will throw a compilation error. Here an example:

    package edu.ltmj.clases;
public class Prueba {
    public static final int X = 10;
}

    package edu.ltmj.interfaces;
public interface Demo {
    int X = 20;
}

    package  edu.ltmj.main;
import static edu.ltmj.clases.Prueba.X;
import static edu.ltmj.interfaces.Demo.X;

public class Main {
    public static void main (String[] args) {
        int x = X; //error de compilación 
    }
}

    For these cases, it is resolved using the class and name of the field to use. For the case above, a possible solution is:

    //se agrega el import de la clase a utilizar
import edu.ltmj.interfaces.Demo;

//se llama al campo relevante 
int x = Demo.X;

    Another very important point is when showing snippets or code fragments to your colleagues or online where you use static fields, make sure you add the import staticnecessary ones, especially when showing code from libraries that are not as well known or for the documentation of how to use one. library you have created.

    • 2

  2. As far as I know there is no contraindication, I think it is a clear improvement for reading the code, for example with the Guava library, use of Preconditions :

    Preconditions.checkArgument(valor!=null);

    against

    checkArgument(valor!=null);

    I think it's much more readable.

    • 1