Re: Generics pains

From:
 Owen Jacobson <angrybaldguy@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 26 Jun 2007 15:17:17 -0700
Message-ID:
<1182896237.121305.149920@n2g2000hse.googlegroups.com>
On Jun 25, 7:07 pm, Joshua Cranmer <Pidgeo...@verizon.net> wrote:

I am trying to create an options class that manages options for a
project. In this class, the options are internally stored as Strings that
can be cast to (depending on circumstances) integers, booleans, or even
enums. However, I am having trouble getting the code to compile:

public final class Options {
    private Options() {}
    private static HashMap<String, String> opts = new HashMap<String,
String>();
    private static HashMap<String, Class<?>> types = new HashMap<String,
Class<?>>();
    public static String getOption(String name) {
        return opts.get(name);
    }

    public static <T extends Enum<T>> T getAsEnum(String name) {
        Class<?> c = types.get(name);
        if (!c.isEnum())
            throw new RuntimeException("Option "+name+" is not an enum!");
        Class<T> ec = c.asSubclass(Enum.class);
        return Enum.valueOf(ec, getOption(name));
    }

}

The exact error:
C:\Documents and Settings\Josh\Desktop\Programming\Java\Decompiler_new
\util\Options.java:43: incompatible types
found : java.lang.Class<capture of ? extends java.lang.Enum>
required: java.lang.Class<T>
               Class<T> ec = c.asSubclass(Enum.class);


....

P.S. I know my error-handling is as of right now unacceptable; I am going
to start fixing that once I implement my logger, for which I need my
getAsEnum function to work.


I realize you're writing a completely general Options class, but the
only actual use you've shown so far is logging... Is there a reason
not to use log4j, which has enough logging levels and configurability
to cover what it looks like you're trying to do?

Owen

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