Is java installed in my database?

Check the following views to confirm whether or not java is a part of your Oracle installation:

ALL_REGISTRY_BANNERS displays the valid components loaded into the database.

SELECT * FROM ALL_REGISTRY_BANNERS
WHERE   BANNER LIKE INITCAP('%Java%') 
OR      BANNER LIKE UPPER('%JAVA%');

If java is installed, the query would typically return:

BANNER
--------------------------------------------------------------------------------
JServer JAVA Virtual Machine Release 11.1.0.7.0 - Production
Oracle Database Java Packages Release 11.1.0.7.0 - Production

DBA_REGISTRY displays information about the components loaded into the database.

SELECT  COMP_NAME,VERSION,STATUS 
FROM    DBA_REGISTRY 
WHERE   COMP_NAME LIKE INITCAP('%Java%') 
OR      COMP_NAME LIKE UPPER('%JAVA%');

If java is installed, the query would typically return:

COMP_NAME                                VERSION              STATUS
---------------------------------------- -------------------- ---------------------------------
JServer JAVA Virtual Machine             11.1.0.7.0           VALID
Oracle Database Java Packages            11.1.0.7.0           VALID

V$OPTION lists database options and features.
Some options must be separately purchased and installed, while other features come with the product and are enabled based on the product that is running (Standard Edition, Enterprise Edition, or Personal Oracle).

SELECT * FROM V$OPTION 
WHERE PARAMETER = 'Java';

Source: Oracle Documentation