We have a JDK that's installed in mixed mode, which I assume accommodates both 32-bit and 64-bit applications. Is there something special I need to do in order to compile it as a 64-bit application? Do I create a setting at the ant build file or compiler switch?
No. Java bytecode is completely independent of the underlying platform - it doesn't matter if the operating system is 32-bit or 64-bit. There is no 32-bit and 64-bit Java code.
"Mixed mode" does not mean that it accommodates 32-bit and 64-bit applications. It means that it runs in interpreted mode (i.e. your Java byte code is interpreted and executed) as well as JIT-compiled mode (your Java code is translated to native machine code and executed) at the same time; the JIT compiler will decide which parts are worth compiling to native code to make them run faster. This is the normal way that the JVM works. There is a way to run it in purely interpreted mode, but that is normally not useful because it will make your program run very slow.
Thanks for your response. I had asked this because I was asked to compile a Java application to target a 64-bit version of Weblogic or Tomcat. There are 64-bit versions available of these web servers. I just didn't know if I had to do anything on my end to ensure that the application took advantage of the 64-bit web server. The OS I am compiling on is 64-bit SUN Sparc and the JVM is also 64-bit. So I would assume I'm good to go with this.
Maybe Weblogic and Tomcat come with some native components that are 32-bit or 64-bit specific, but both these app servers are for the largest part written in Java and are not specific for 32-bit or 64-bit.
For your Java webapp there's absolutely nothing that you'll have to do or change; it doesn't matter if the underlying JVM or OS is 32-bit or 64-bit.