Berkeley CSUA MOTD:Entry 41399
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2025/07/08 [General] UID:1000 Activity:popular
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2006/1/17-20 [Computer/SW/Languages/Java, Computer/SW/Compilers] UID:41399 Activity:low
1/17    Java compiler help please.  I have some code like this:
        import com.foocorp.foolibrary;
        class myClass {
          private static final boolean useFooLib=false;
          {
            if(useFooLib)
              foolibrary.FooClass.doStuff();
          }
        }
        And the problem is that if I turn off useFooLib and try to compile
        with out foolibrary.jar the compile fails.  Is there any way I can make
        this work without distributing foolibrary.jar with every build?
        \_ I haven't had to think about this for a while, but maybe you
           can use a custom class loader?  What about reflection?
           \_ Yeah, I went with that, starting with Class.forName() as
              suggested below.  Between reflection and commenting out multiple
              blocks it seemed like the lesser of two evils. Thanks.  -OP
              \_ Interesting I was not aware that javac allows you to delay
                 type checking, to see whether method doStuff() exists or not.
                 Thanks for pointing this out. Motd is great!
                 \_ Um, that's not what I said.  I used Class.forName() to
                    dynamically load the class, then I used reflection to
                    get the methods I want, then invoke those methods on
                    the class object (thet are static methods).
              \_ I think the cleaner way to do this is to create an
                 interface -- FooClassInterface. Include that in your
                 normal code path, but you don't need to provide an
                 implementation. Make FooClass implement that interface
                 then you can do:
                   if (useFooLib)
                        FooClassInterface foo =
                          (FooClassInterface) Class.forName(...).newInstance();
                        foo.doStuff();
                 I think that's preferable. - guy who made below suggestion.
                 \_ Won't work.  FooClass is a partially-obfuscated JAR
                    licensed from another company.
        \_ Java is not C. If this were C, the statement "if ..." would be seen
           as dead code due to constant propagation. However javac does flow
           analysis before optimizations so requires method/var resolution
           first and you can't possibly compile with safety without foolibrary.
           If you must include such a dead code, manually comment out the dead
           code or just include the foolibrary.class|java with the distro.
           Go compilers!!!
        \_ Don't import foolibrary. Do this:
                if (useFooLib)
                  Class.forName("com.foocorp.foolibrary.FooClass").doStuff();
2025/07/08 [General] UID:1000 Activity:popular
7/8     

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