This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I think Tomcat moved to JSE5 from Tomcat version 5.5 but you could install a compatability patch to allow it to use JSE 1.4.
Since the problem is with Struts I think you're just going to have to run Tomcat using JSE5 (or 6) but should still be able to compile against JSE 1.4