Sun Java System Application Server Platform Edition 9 Upgrade and Migration Guide

Source Compatibility

Downward source compatibility is not supported. If source files use new Java EE APIs, they are not usable with an earlier version of the Java platform.

In general, the policy is as follows:

Deprecated APIs are methods and classes that are supported only for backward compatibility, and the compiler generates a warning message whenever one of these is used, unless the -nowarn command-line option is used. It is recommended that programs be modified to eliminate the use of deprecated methods and classes, though there are no current plans to remove such methods and classes entirely from the system.