Java earned a place on enterprise technology stack for quite some time already and we successfully use it for various tasks like: reporting, integration and tooling.
There are a number of great reporting engines available in Java that we've used with success for building reporting solutions: Birt, Jasper Reports, Pentaho.
Any enterprise application in today's world requires some sort of integration with the ecosystem around it. Be it simple data integration through ETL tools like Pentaho or Talend, or service integration through web-services/rest Java offers a number of products and frameworks that can fulfil any integration needs.
The openness and plug-able nature of the Eclipse platform makes it a perfect choice for building development tools and extend existing ones like Birt, Bonita BPM or Progress Developer Studio for OpenEdge.
Building modelling tools is a breeze using UML, GMF together with language recognition frameworks like ANTLR and XTEXT.