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Groups > comp.lang.java.programmer > #31700

Re: get a list of classes at runtime

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On Wednesday, May 13, 2015 at 10:07:19 AM UTC-4, Eric Sosman wrote:
> On 5/13/2015 8:47 AM, Philipp Kraus wrote:
> > Hello,
> >
> >
> > I would like to get a list of all loadable classes, because I create an
> > UI which should be list on the user input, which classes are existst
> > e.g. the user types ABC and I will get the full class name with
> > packages, e.g. package1.subpackage.ABC and package2.ABC
> 
>      "All loadable classes" is a potentially infinite set, since a class
> loader might look almost anywhere to find a class -- it might even
> synthesize a class by filling a byte[] array with bytecodes and then
> loading it.  But perhaps your goal is not quite so ambitious ...
> 
> > I have taken a look into https://github.com/ronmamo/reflections but I
> > don't find a call to filter all class names. How I can get the full
> > class name list during runtime (all my classes are stored within a Jar
> > file and the search should be also add the Java base classes e.g. String)
> 
>      AFAIK, the JVM has no record of potentially loadable classes that
> have not been loaded (there are probably some special-case exceptions
> like String and Class and Throwable, but they'll all have been loaded
> well before your code runs).  If I'm right, it means the only way you
> can find the not-yet-loaded classes is to rummage through the JAR's (or
> other sources) for yourself.  You presumably know where to find your
> own JAR's and things; I believe all "base classes" reside in rt.jar.
> I don't know of a convenient way to find "the" rt.jar that your JVM
> happens to be using; the best I can think of is to read the java.home
> System property and search from there. (Or from sun.boot.class.path,
> but I'm not certain that's a property all JVM's will define.)
> 
>      Anyhow: Once you've found the JAR's, you'll read their directories,
> do a little reformatting, and filter as you please.
> 
> -- 
> esosman@comcast-dot-net.invalid
> "Don't be afraid of work. Make work afraid of you." -- TLM

To find the rt.jar your IDE would just have to specify where the rt.jar is.
Normally to build a project in Eclipse you add "JRE System Library" to the build path.  You'll see that as a folder in the Package Explorer.  You can expand that folder.  I don't know if Oracle/Sun publishes a list of which jars to include or where they get it but my Eclipse project using Java 8 update 40 has 18 jars listed there.

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get a list of classes at runtime Philipp Kraus <philipp.kraus@flashpixx.de> - 2015-05-13 14:47 +0200
  Re: get a list of classes at runtime Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-05-13 10:06 -0400
    Re: get a list of classes at runtime Philipp Kraus <philipp.kraus@flashpixx.de> - 2015-05-13 16:14 +0200
      Re: get a list of classes at runtime Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-05-13 11:23 -0400
        Re: get a list of classes at runtime Arne Vajhøj <arne@vajhoej.dk> - 2015-05-17 19:29 -0400
      Re: get a list of classes at runtime Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2015-05-13 22:15 -0500
    Re: get a list of classes at runtime e.d.programmer@gmail.com - 2015-05-13 08:59 -0700
      Re: get a list of classes at runtime Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-05-13 16:05 -0400
        Re: get a list of classes at runtime Martin Gregorie <martin@address-in-sig.invalid> - 2015-05-13 22:43 +0000
  Re: get a list of classes at runtime Joerg Meier <joergmmeier@arcor.de> - 2015-05-13 16:20 +0200
  Re: get a list of classes at runtime j4n bur53 <janburse@fastmail.fm> - 2015-05-13 17:47 +0200
  Re: get a list of classes at runtime Arne Vajhøj <arne@vajhoej.dk> - 2015-05-17 19:09 -0400

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