static as only identifier

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Philipp - 12 Apr 2007 17:43 GMT

Hello
I've been looking around the apache Harmony java files and found a
statement which I have never seen before.
package: org.apache.harmony.x.imageio.plugins.jpeg
file: JPEGImageWriter.java

public class JPEGImageWriter extends ImageWriter {
//ctor and member vars are here

static {
System.loadLibrary("jpegencoder");
initWriterIds(ImageOutputStream.class);
}

// rest of class methods is here
}

What's this "static" without a name or identifier? How is it used?
What's it for?

Thanks for your answers.
Phil

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Eric Sosman - 12 Apr 2007 18:15 GMT

Philipp wrote On 04/12/07 12:43,:

> Hello
> I've been looking around the apache Harmony java files and found a
[quoted text clipped - 15 lines]
> What's this "static" without a name or identifier? How is it used?
> What's it for?

Look up "static initializer" or "static initialization
block" in your Java textbook. In the snippet you've shown,
the code inside the { } will be executed once, during the
initialization of the class.

Signature

Eric.Sosman@sun.com

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Martijn - 12 Apr 2007 18:38 GMT

> Philipp wrote On 04/12/07 12:43,:
>> public class JPEGImageWriter extends ImageWriter {
[quoted text clipped - 15 lines]
> the code inside the { } will be executed once, during the
> initialization of the class.

This way you can have static objects, but still have the opportunity to
properly initialize them without special constructs like factories and the
sorts.

Signature

Martijn
http://www.sereneconcepts.nl

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Mark Space - 12 Apr 2007 18:56 GMT

> Look up "static initializer" or "static initialization
> block" in your Java textbook. In the snippet you've shown,
> the code inside the { } will be executed once, during the
> initialization of the class.

In Java parlance, "initialization" means when the class is loaded by the
classloader.

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Oliver Wong - 12 Apr 2007 18:31 GMT

> public class JPEGImageWriter extends ImageWriter {
> //ctor and member vars are here
[quoted text clipped - 9 lines]
> What's this "static" without a name or identifier? How is it used?
> What's it for?

See http://java.sun.com/docs/books/tutorial/java/javaOO/initial.html

- Oliver

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Greg R. Broderick - 12 Apr 2007 20:51 GMT

Philipp <sicsicsic@freesurf.ch> wrote in news:1176396236_1015
@sicinfo3.epfl.ch:

> What's this "static" without a name or identifier? How is it used?
> What's it for?

It is a static initializer for the class.

c.f. <http://www.developer.com/java/other/article.php/2238491>

Cheers!

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static as only identifier

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