Java Static Import With Examples

With Java static import feature, which was added in Java 5, you can access static members (fields and methods defined as public static) of a class without qualifying them with class name.

Table of contents

How to use static import in Java
Java static import example
Advantages of using static import
Drawbacks of using static import
Static import ambiguity

How to use static import in Java

Generally if you need to access any static member (static field or method) of a class you need to qualify it with the class name.

For example syntax for accessing a static method-

ClassName.static_method()

Static import helps with shortening the syntax required to use a static member. Using static import you can import static member that is needed in the class.

Syntax for static import of static field

import static package_name.className.static_field;

Syntax for static import of static method

import static package_name.className.static_method;

You can also import all the static members of a class using the following syntax-

import static package_name.className.*;

Java static import example

Math class in Java has many static methods, first let’s see how we can use those static methods if static import is not used.

public class MathDemo {
  public static void main(String[] args) {
    double value = Math.pow(3, 2);
    System.out.println("Square of 3 is- " + value);
    double sqrt = Math.sqrt(3);
    System.out.println("Square root of 3 is- " + sqrt);
  }
}

Output

Square of 3 is- 9.0
Square root of 3 is- 1.7320508075688772

Example using static import

By using static import you don’t need to qualify methods with class name.

import static java.lang.Math.*;
public class MathDemo {
  public static void main(String[] args) {
    // Qualifying static method is not required
    double value = pow(3, 2);
    System.out.println("Square of 3 is- " + value);
    double sqrt = sqrt(3);
    System.out.println("Square root of 3 is- " + sqrt);
  }
}

As you can see in the code static import is done for all the static members of the Math class so there is no need to qualify methods of the Math class.

You could have also just imported the required methods.

import static java.lang.Math.pow;
import static java.lang.Math.sqrt;

Advantages of using static import

If you are using static members from a class or two with in your code then static import helps in making the code concise.
Static import also helps you to avoid creating an interface having only constants and then implementing that interface which is considered a constant interface anti pattern. You can as well define static fields with in a class and then do a static import of static members of that class.

Drawbacks of using static import

If you are doing static import from lots of classes then it creates confusion as it is hard to know which class any particular static member belong to.
Static import may also cause ambiguity if two static members of the same name are imported from different classes.

Static import ambiguity

If two static members of the same name are imported from different classes then compiler won’t be able to decide which one to use and throw an error.

For example consider the following code where static members of both Integer and Long are imported using static import. Now using the static method valueOf(String) and static field MAX_VALUE results in ambiguity as these members are present in both of the classes.

That's all for the topic Java Static Import With Examples. If something is missing or you have something to share about the topic please write a comment.

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January 7, 2024