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Groups > comp.lang.java.programmer > #31698

Re: get a list of classes at runtime

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On 5/13/2015 10:14 AM, Philipp Kraus wrote:
> On 2015-05-13 14:06:53 +0000, Eric Sosman said:
>
>> On 5/13/2015 8:47 AM, Philipp Kraus wrote:
>>
>>      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.
>
> I think so, but how do IDEs like IntelliJ or Eclipse this call? If I
> write into the code editor
> something a dialog is show, which lists all possibility classes.
> So imho I need to run over the Jar, create an index of all class files
> and use a pattern structure to
> match the names.

     That's what I would do.  Note that a JAR will have directory entries
for *all* its classes, including nested classes, private classes, and
package-private classes.  You can filter out the nested classes by their
funny-looking names, but if you also want to filter based on access I
can think of only two ways:

     - Read the class file (the format is described in the JVM spec).

     - Load the class (use the three-argument form of Class.forName()
       if you don't want to initialize it) and use getModifiers().

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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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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