Last updated at 1:12 p.m. PT.
SAN FRANCISCO -- While the Java language is free to use and that isn't being contested by either Google or Oracle, one of the key tasks Oracle needs to accomplish if it wants to win its intellectual property lawsuit is prove the value of Java APIs.
Part of that task has fallen on Mark Reinhold, chief architect of the Java platform group at Oracle, who testified as an expert witness during the Oracle-Google trial at the U.S District Court, Northern District of California, on Wednesday.
Reinhold previously worked at Sun Microsystems, from when he joined in 1996 until the Oracle acquisition in 2010. Reinhold has worked on the Java platform for the last 16 years. He explained that he is referred to as an "architect" because he looks after the coherence of the Java platform as a whole so that it "continues to make sense."
Reinhold informed the jury that a Java class library is a type of software library of pre-written programs that are pre-tested with pure documentation, which can be then referenced in developers' own codes.
Part of Oracle's case against Google rests on the argument that Google engineers knowingly copied select strips of code, line for line, from Java APIs without a license to do so.
However, explaining the Java class library system to the jury became a source of debate between the plaintiff and defendant lawyers in the case as Google's legal team objected to Reinhold explaining this system in detail with a slideshow.
Nevertheless, Judge William Alsup overruled the objection and let Reinhold continue.
Most importantly (at least to Oracle's case), Reinhold affirmed that the structure of Java APIs and structure of the Java class libraries are exactly the same because they are built from the same source code.
Specifically, there are 37 Java APIs at question in this suit of being used in Android illegally -- including two files in APIs that contain nine lines of arranged checked code, accused here by Oracle of being assembled line by line and copied. Furthermore, there are two more files where some comments in the files are also accused of being copied.
In earlier testimony, Oracle chief corporate architect Edward Screven testified as a witness on behalf of Oracle, reiterating the specific value of Java to Oracle.
In fact, Screven asserted that he told Oracle CEO Larry Ellison in 2009 that "we should buy Sun for no other reason than Java," and that "Java was easily worth the purchase price."
Oracle is in the hardware and software businesses now. In software, people pay us for licenses to use our software. It's important to us that we actually enforce intellectual property rights around our software. Otherwise, people would take our software without paying us, undermining our business model.
In an interesting side note, Reinhold mentioned that the name "Java" was chosen for the language as a replacement for the term "Oak," which had already nabbed by another technology company. During a discussion meeting about the name, it simply came about when someone came in with a cup of -- wait for it -- java.
This story originally appeared at ZDNet's Between the Lines under the headline "Oracle exec: No other reason to buy Sun except for Java."