NEW YORK (AP) ― Oracle Corp. received another setback Thursday as a federal judge in San Francisco undermined a central part of the company’s multimillion dollar case against Google Inc. over its Android software for mobile devices.

Oracle had accused Google of copyright infringement in using “application programming interfaces,” or APIs, that help Oracle’s Java software work effectively. A jury found Google infringed on those APIs on May 7, but it couldn’t agree on whether Google was covered under “fair use” protections in U.S. law. Without a fair-use determination, Oracle wasn’t able to extract huge sums from Google.

Now, U.S. District Judge William Alsup said Google’s use of the APIs wasn’t covered by copyright law in the first place.

The effect of Thursday’s ruling is limited because a jury had earlier reached an impasse on the issue of fair use. But the ruling could be important in any appeals.

Oracle said it will appeal the ruling.

Android now powers more than 300 million smartphones and tablet computers.

Those devices are the chief competitors to Apple’s iPhones and iPads. Google has driven the adoption of Android by giving the software away to manufacturers of phones and tablets.

That would have been more difficult for Google to keep doing if the court had found that Google needed to pay Oracle millions of dollars to license Java technology.

The jury in the case had been asked to rule on the infringement and fair use questions on the assumption that the APIs were copyrightable. Alsup deferred a ruling on the broader copyright question until after the trial, which ended May 23.

Alsup ruled Thursday that Google didn’t use Oracle’s exact programming code in Android, but rather wrote its own code to produce the same functions.

Although Google used some of the same phrases in the code, Alsup said it had to do so to maintain interoperability. Names, titles and short phrases aren’t covered by copyright, and Google’s use of those phrases amounted to that, he said.