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by syjer 3928 days ago
>Except they don't mention at all how a module system should lead to faster boot times.

They will switch from the basic jar (zip) format to a more optimized one. Additionally, with a modularized jre, it will load less modules (who use corba?). I'm quite sure there are additional reasons, but it's the 2 that I remember.
2 comments
needusername 3928 days ago
> They will switch from the basic jar (zip) format to a more optimized one.

Straight from the article:

> A modular JAR file is like an ordinary JAR file in all possible ways, except that it also includes a module-info.class file in its root directory.

> A modular JAR file can be used as a module, in which case its module-info.class file is taken to contain the module’s declaration. It can, alternatively, be placed on the ordinary class path, in which case its module-info.class file is ignored

So no.

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syjer 3928 days ago
That's why it's called a modular jar. There is also this "jmod" file described as:

"For the purpose of modularizing the Java SE Platform’s reference implementation, the JDK, we will introduce a new artifact format that goes beyond JAR files to accommodate native code, configuration files, and other kinds of data that do not fit naturally, if at all, into JAR files. This format leverages another advantage of expressing module declarations in source files and compiling them into class files, namely that class files are independent of any particular artifact format. Whether this new format, provisionally named “JMOD,” should be standardized is an open question."

Edit: from http://mreinhold.org/blog/jigsaw-modular-images

"The internal files rt.jar, tools.jar, and dt.jar have been removed. The content of these files is now stored in a more efficient format in implementation-private files in the lib directory."

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needusername 3928 days ago
> For the purpose of modularizing the Java SE Platform’s reference implementation, .... Whether this new format, provisionally named “JMOD,” should be standardized is an open question.

That just talks about the JDK. There is no promise that normal applications can use this format.

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chrisseaton 3928 days ago
The JVM already only loads classes on demand so if you don't use Corba it doesn't have any impact on you (maybe minuscule extra seek time reading the JAR).
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hinkley 3928 days ago
The jar files used to be memory mapped, and as far as I'm aware they still are. So there should be a noticeable improvement in seek time by eliminating never-used files.

You could also perhaps be looking at a situation in the future where the JRE can selectively exclude things at install time, which would be nice.

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syjer 3928 days ago
Clear, but the single rt.jar will be replaced with a more convenient representation, so, as you said, the seek time will be reduced.
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