Speaking on the witness stand earlier in the week, Safra A. Catz, the co-chief executive of Oracle, called Java, the open-source product Google is accused of taking, “the single most important asset Oracle acquired” in its 39-year history, and spoke of billions in lost revenue as a result of Google’s actions. Oracle picked up Java when it purchased Sun Microsystems for $7.4 billion in 2010.

The fight between Oracle and Google began that year as a patent and copyright dispute, and in one phase or another it has involved many of the best-known names of Silicon Valley.

The initial case was decided largely in favor of Google in 2012, and the patent claims were dismissed. But in 2014 a federal appeals court found certain parts of Java were protected by copyright. When the Supreme Court refused to hear an appeal of that decision last year, the case was sent back to federal court.

This trial, which began last week, has followed a tangle of careers as well as code. Eric Schmidt, the executive chairman of Alphabet, testified on his time working on Java when he was at Sun, and his knowledge of Apple’s iPhone developments when he sat on the Apple board. Andy Rubin, who led the Android efforts at Google and also testified, had worked at Apple early in his career, and used Java at Danger, another phone company he co-founded. Mr. Rubin has since left Google, and is working on robots and artificial intelligence.

Lawrence J. Ellison, co-founder and now executive chairman of Oracle, appeared in a taped deposition about acquiring assets of Sun. Though it was not mentioned in the testimony, Sun fell on hard times after the dot-com boom largely because of competition from another open-source software project, Linux.

Mr. Ellison was also close friends with Steven P. Jobs, Apple’s co-founder, who was outraged when Google revealed its plans for an iPhone competitor that looked a lot like the iPhone.

There were even glimpses of frosty social exchanges. Ms. Catz testified to running into Google’s corporate lawyer at a bat mitzvah. “‘Google is a very innovative company,’” she recalled him saying. “‘The old rules do not apply to us.’”