Eclipse Project Access Java Core Classes On Mac OS X

Am running Eclipse on Mac OS X but for some crazy reason it just can't find my Java base classes like ArrayList etc... I just the Install JRE u开发者_开发百科nder Preferences and there is a valid JDK that got all the classes correct like point to classes.jar etc... Any idea what can be wrong? And yes I did do a Clean, it just can't build.

Eclipse Helios, latest Java 6, Snow Leopard Mac OS X

It is likely that your Eclipse uses the Java JRE and not the JDK. You need to point Eclipse to where your JDK is installed.

Go to Preferences -> Java -> Installed JREs and Add your JDK directory. Then make sure that you uncheck (or remove) the previous JRE. That should allow you to see the base classes.