SAN FRANCISCO — Oracle and Google’s billionaire CEOs have spent nearly 20 hours this week holed up in a federal courthouse with their lawyers and other top company executives for court-ordered settlement talks. And the pair may be required to go back for more.

The closed-door sessions with San Jose U.S. Magistrate Judge Paul Grewal went on for more than nine hours on Monday and for another 10 hours Wednesday. They haven’t produced a settlement in the billion- dollar patent dispute over Java technology, according to court filings. But a filing Wednesday night suggests they haven’t been a waste of time.