Sun Java System Application Server 9 requires J2SE 5.0 or greater as the underlying JVM. If you want to switch from one Java version to another, perform the following general steps. (Windows and Unix)
Download the Java SDK (not the JRE) and install it on your system, if you have not already done so.
The Java SDK can be downloaded from http://java.sun.com/j2se.
Completely stop the Application Server.
You can use the following command line:
Alternatively, you can use the Administration Console GUI:
Edit the install_dir/config/asenv.conf file (asenv.bat on Windows), changing the value for AS_JAVA to point to the new J2SE home directory.
Edit the as-install/samples/common.properties file, changing the line beginning com.sun.aas.javaRoot... to reference the new J2SE home directory.
Restart the Application Server.