Downward source compatibility is not supported. If source files use new J2EE APIs, they are not usable with an earlier version of the J2EE platform.
In general, the policy is as follows:
Maintenance releases do not introduce any new APIs, so they maintain source-compatibility with one another. However, since J2EE is based on J2SE, a new Application Server release may include a new version of J2SE. For more information, refer to the J2SE document on compatibility issues:
Functionality releases and major releases maintain upwards but not downwards source-compatibility.
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 plans to remove such methods and classes entirely.