Project fails to build in Eclipse under Mac

So, I finally figured out how to update Java in Mac and managed to get my class with a SwingWorker work; previously, Java was complaining because I had Java 1.5 and 1.5 does not have SwingWorker. I wasn't able to change the default JRE in Mac though; I just linked the JRE 6 library in Eclipse so I can build. It is now happy even in the presence of SwingWorker.

However, when I try to build my project, I get the following error:

Errors occurred during the build.
Errors running builder 'Integrated External Tool Builder' on project 'Pr开发者_运维百科ojectName'.
Exception occurred executing command line.
/Users/lab/Documents/workspace/ProjectName/.project: cannot execute
Exception occurred executing command line.
/Users/lab/Documents/workspace/ProjectName/.project: cannot execute

Anyone knows this error? I've tried cleaning the project then building again but to no avail. Any suggestions?

Thanks!

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As you said, you did not manage to set the default JRE version in Eclipse - this might be a problem, as simply adding the Java 6 libs might not work (e.g. classes compiled with Java 6 can be incompatible with Java 5 because of different byte code version).

First of all, open Preferences, and go to the Java/Installed JRE's page, and make sure that the newly installed Java 6 is available here. If not, add it as a Mac OSX VM. This has to be done manually, as Eclipse does not look for additional VMs after the first launch.

After the JRE is installed, update your project settings: right click on your project, select Properties, and in the Java build path page make sure that Java 6 is set as the JVM on the build tab - if not, then edit the entry, and select a Java VM 6 execution environment.

Finally (this step might not be needed), open the Run configuration, (Run/Run configurations... in menu), select your projects configuration, and on the main page make sure, that for runtime also a Java SE 6 VM or execution environment is selected.