Time to time you have a java project, which uses an old version of the JRE compiler. Installing old java versions on OS X is quite tricky and not necessary. You can use the compiler compliance level feature in Eclipse IDE. This setting just tells the compiler to pretend it’s a different version of Java.
In this blog post I will start with something simple. These instructions are for beginners who have no experience with Java and don’t know how to deploy a java web application archive file (.war) on Tomcat on OS X (should work on Linux too).