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Oracle FAQ page contains link to the Oracle page containing a list of driver files of different database versions. It also contains a link to driver compatibility matrix, though that page is unfortunately clearly outdated, as it doesn't contain any information on the Oracle 12 JDBC driver.
I'd suggest to use the either the ojdbc6.jar file that comes with the Oracle 11g Release 2 database (it will work with Java 7), or the Java 7 driver was released with the 12c version of the database (ojdbc7.jar). I honestly believe that the 12c version of the driver is backwards compatible with Oracle 10g (Oracle's policy for years was that drivers and databases are mutually compatible if they are two versions apart, if not more), but I haven't found it stated explicitly anywhere yet.