MENLO PARK, Calif. (AP) — A federal appeals court has overturned a decision in a long-running legal battle over whether Google infringed on Oracle's Java programming language to build its hugely popular mobile operating system, Android.

The court said Google's use of Java was "not fair" and sent the case back to trial to determine damages.

Oracle had originally sought $9 billion. The court said Android helped Google earn $42 billion in advertising revenue since the first Android phone went on sale in 2008.

Oracle hailed Tuesday's ruling, saying the opinion by the U.S. Court of Appeals for the Federal District upholds fundamental principles of copyright law.

A Google spokesman said the ruling was disappointing and that it would make apps and online services more expensive. The company is considering its options.