To start an application which requires X server connection in Unix from a text client (like Putty, ssh) the following property can be added to the JVM:
          java -Djava.awt.headless=true ...

This fixed the following errors:
   In Tomcat server:  X connection to localhost:10.0 broken (explicit kill or server shutdown).
   In a Swing application: No X11 DISPLAY variable was set, but this program performed an operation which requires it.