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Thread: How to use static imports

  1. #1
    Super Moderator helloworld922's Avatar
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    Default How to use static imports

    Ever got tired of having to type Math.PI whenever you want to access PI?

    There is a way to get around this (edit: must be Java 1.5 or new) by using static imports. Basically, static imports allow you to import static members of a class to be used without the class qualifier.

    example:

    // import PI statically from Math.PI
    import static java.lang.Math.PI;
     
    public class MyClass
    {
        public static void main(String[] args)
        {
            // we can use PI without having to type Math.PI
            System.out.println("pi is " + PI);
    }

    It is possible to "group import" with the static qualifier, too.

    // import all static members from Math
    import static java.lang.Math.*;
     
    public class MyClass
    {
        public static void main(String[] args)
        {
            System.out.println("cos: " + cos(1.0));
            System.out.println("pi: " + PI);
        }
    }

    WARNING

    You should only use this feature SPARINGLY! It can become extremely confusing if you import every static field from other classes in this manner. Also note that this method only imports the static fields/members, you still need to import the class in order to instantiate that class.

    You may not statically import all static members from a package, and you must qualify the members you want to import from the class.


    // illegal: java.lang is a package
    import static java.lang.*;
    // illegal: you must qualify which fields from the class you want to import
    import static java.lang.math;

    edit:

    Static imports require Java 1.5 or newer
    Last edited by helloworld922; July 3rd, 2010 at 02:39 PM.

  2. The Following 2 Users Say Thank You to helloworld922 For This Useful Post:

    copeg (July 3rd, 2010), JavaPF (July 3rd, 2010)


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