docx4j is intended to run on Java 1.5 (provided JAXB RI is on your path).
To support this, in the 2.7.0 release candidate maven pom.xml, we have:
<source>1.6</source>
<target>1.5</target>
The objective is to generate a jar which is compatible with Java 1.5, whilst at the same time allowing @Override annotations in the source code on methods which merely implement an interface (Java 6 allows this, but 1.5 gives an error).
When I played around with ...