In the J2ME world of wildly non-conforming implementations, conditional compilation is the norm. Sun even admited it by adding "configurations" (IIRC) to NetBeans 5. EclipseMe (Now the official Eclipse Mobile Tools for Java project--MTJ) has support for it, as does the Antenna extension to Ant.
The most common method currently is to use a construction such as //#if CONDITIONAL ... //#endif This shields the conditional statement from language-aware but conditional-unaware editors. The build system then comments out the intervening lines of code if the condition is not met. I've used everything from ant processing to running the full Java code (and even XML files) through the C++ preprocessor for macro expansion. In Android, especially when trying to maintain two versions of a product (Free vs. Paid, for example) conditional compilation (or parallel code trees) is mandatory because the package names must change (at least in the manifest). This is one case where the if (const) blocks will not work. If there is a better way of handling this, please enlighten us. I haven't yet tackled this problem in the Android dev environment because it tends to disrupt the debug part of the edit-compile-debug- edit cycle. What I have done is to add an eclipse builder to run a perl script to generate a Java interface (in the gen/ directory) that defines constants for build time/number pulled from Team Foundation Server. This allows automatic version stamping for the about screen-- though does not yet modify the version name/number in the manifest. On Mar 30, 9:42 am, Bob Kerns <r...@acm.org> wrote: > You can download a Java decompiler and investigate yourself. I suggest > this one:http://java.decompiler.free.fr/?q=jdgui > > You'll see that it does indeed optimize when it can. > > However, unlike a C file which gets linked into a .so or .dll or an > executable, Java classes may be combined in different ways. > > So it cannot optimize away static final references in other classes, > because those may change. > > However, tools like ProGuard can do so, because they work on an entire > application. > > But remember, once you do something like this, that code can never be > used in a context with a different valiue. > > It virtually never makes sense to do this for conditional compilation > reasons. Sometimes it makes sense to generate code (the Android tools > do in fact generate a couple of files). In the rare case you do need > to eliminate code due to extremely tight performance constraints or > size constraints, I'd recommend the ProGuard route, as it will do a > FAR more thorough job than you can do manually with conditional > compilation. > > On Mar 30, 8:12 am, "Kevin S." <dada...@gmail.com> wrote: > > > > > It really isn't very easy to do this. In general, you can do > > something like > > > public class MyClass > > { > > public static final boolean HAS_CHEEZBURGER=true; > > > public void someMethod() > > { > > if( MyClass.HAS_CHEEZBURGER) > > { > > doCheezburger(); > > } else > > { > > noCheezBurger(); > > } > > } > > > } > > > The compiler I think will see that HAS_CHEEZBURGER is constant and > > can never change, and may optimize away the branch not taken. Perhaps > > some more knowledgeable folk could comment on that. > > > If on the otherhand, you really really think you need to do > > preprocessing using eclipse and Java, you can. See the following > > link. > > >http://www.boldinventions.com/index.php?option=com_content&view=artic... > > > -Kevin > > > On Mar 30, 5:57 am, Dilip Dilip <dileep2m...@gmail.com> wrote: > > > > Hi All, > > > How to do conditional compilation in JAVA. > > > > something like in C, C++ : > > > > #ifdef TRUE_CONDITION > > > > #else > > > > #endif > > > > Thanks and Regards, > > > Dileep- Hide quoted text - > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe, reply using "remove me" as the subject.
