Hmm… ok. Next you could try investigating your Java tools.
First, you should see if you have Java 6 at the least. Judging from the warnings you were getting, it looks like you might have Java 5.
Type javac -version at the command line. If you’re output is like the following, then you should have the latest Java 6 JDK installed.
$ javac -version javac 1.6.0\_65
If you don’t have Java JDK 6, From Oracle’s FAQ page:
For Java versions 6 and below, Apple supplies their own version of Java. For Mac OS X 10.6 and below, use the Software Update feature (available on the Apple menu) to check that you have the most up-to-date version of Java 6 for your Mac. For issues related to Apple Java 6 on Mac, contact Apple Support.
After getting the latest version of Java JDK 6 installed, verify that your JAVA_HOME environment variable is set correctly. Do this by typing $JAVA_HOME at the command line. The output should be like the following:
$ $JAVA\_HOME -bash: /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home: is a directory
If this isn’t correct, change it in your .bash_profile as mentioned before.
Assuming all this is now correct, try compiling the plugin again and see if it works.