Java 1.6 is required on the application server machine. J2SDK 1.6.0_37 is certified for WebOffice 10 R3.
The version can be downloaded via:
http://www.oracle.com/technetwork/java/javase/downloads/index.html

Choose the correct installation patch for the Java directory
Note: Using the 64bit version of Java requires a 64bit OS and Tomcat in 64bit mode.