What is static import in Java?

We will discuss about static import in Java. The static import construct allows unqualified access to static members without inheriting from the type containing the static members. Instead, the program imports the members, either individually:

import static java.lang.Math.PI;

or all at once from a particular package.

import static java.lang.Math.*;

Once the static members have been imported, they may be used without qualification:

double r = cos(PI * theta);

The static import declaration is analogous to the normal import declaration. Where the normal import declaration imports classes from packages, allowing them to be used without package qualification, the static import declaration imports static members from classes, allowing them to be used without class qualification.

So when should you use static import?
  • Only use it when you’d otherwise be tempted to declare local copies of constants, or to abuse inheritance (the Constant Interface Antipattern). In other words, use it when you require frequent access to static members from one or two classes.
  • If you overuse the static import feature, it can make your program unreadable and unmaintainable, polluting its namespace with all the static members you import.
  • Readers of your code (including you, a few months after you wrote it) will not know which class a static member comes from.
  • Importing all of the static members from a class can be particularly harmful to readability; if you need only one or two members, import them individually.
  • Used appropriately, static import can make your program more readable, by removing the boilerplate of repetition of class names.

For example,

import static java.lang.System.out;
public class StaticImport {
    public static void main(String[] args) {
        out.println("Hello");
    }
}

Thanks for reading.

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