What is a good use case for static import of methods?

java

best-practices

readability

testing

byNikita Barsukov·Sep 4, 2024

Use static imports for commonly used static methods and constants to enhance code where readability remains clear. Ideal cases include:

Mathematical constants: PI or E.
Regularly used utility methods such as max, min, sort.
Testing utility methods like assertThat or fail.

Static imports allow you to drop the class name, resulting in shorter code and greater focus.

Example:

import static java.lang.Math.*;
import static org.junit.Assert.*;

public class MathTests {
    public void testSin() {
        // Without 'Math', we still calculate just fine!
        assertEquals(0, sin(PI)); 
    }
}

In context, sin and PI are plainly recognizable, reducing clutter without sacrificing clarity.

Key principles for static imports

1. Minimize imports: Stick with importing individual members rather than all static members which maintains readability. Instead of import static java.util.Arrays.*; prefer import static java.util.Arrays.sort;.

2. Readability is king: Overusing static imports, especially from different classes, can detract from readability. Use sparingly to avoid confusion.

3. Avoid inheritance temptation: Go for static imports only when you're tempted to extend the class to use its constants or methods.

4. Mind the frequency: Ideally, use static imports for often-used methods or constants. If you're constantly using java.time.Month.*, then static imports would clean up your code.

Applications in testing and utility classes

For testing libraries like JUnit, the assertEquals(expected, actual) is clearer and shorter than Assert.assertEquals(expected, actual), making the code both readable and functional.

Certain well-known utility classes such as Arrays.asList or Collectors.toList can be instantly identified by most Java programmers, thus making it a good candidate for static imports.

However, it's important to remember that development tools like IDEs can show the source of a static import by hovering or clicking on the method, minimizing some readability concerns. , making static imports more useful when used judiciously.

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