Check if package exists at runtime

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Bruce Lee - 27 Jan 2006 07:50 GMT

Is there anyway to check if a package exists at runtime? Class is simple -

try{
Class.forName("java.class1.Class12");
}catch(Exception e){}

but can you do this for a whole package?

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Damian Brunold - 27 Jan 2006 08:00 GMT

> Is there anyway to check if a package exists at runtime? Class is simple -
>
[quoted text clipped - 3 lines]
>
> but can you do this for a whole package?

Package.getPackages() gets all packages known to the callers
ClassLoader. At least this is what the documentation says...

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Robert Klemme - 27 Jan 2006 08:19 GMT

>> Is there anyway to check if a package exists at runtime? Class is
>> simple -
[quoted text clipped - 7 lines]
> Package.getPackages() gets all packages known to the callers
> ClassLoader. At least this is what the documentation says...

public static boolean packageExists(String name) {
return Package.getPackage(name)!=null;
}

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Package.html#getPackage(java.l
ang.String)

robert

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Chris Smith - 27 Jan 2006 15:36 GMT

> public static boolean packageExists(String name) {
> return Package.getPackage(name)!=null;
> }

Note that this will return true ONLY when a class from the package has
already been loaded. It does not somehow check if anything from the
package might be available in the future. That is the JVM's definition
of whether the package exists (it doesn't exist until it's first used),
but it's probably not the definition the OP wanted.

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Stefan Schulz - 27 Jan 2006 11:49 GMT

You can, if the package is sealed, just check if all classes can be
retrieved by Class.forName(). Otherwise, the notion of "whole package"
makes no sense, since there may be any number of classes also living in
that package you have never heared about.

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Check if package exists at runtime

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