"man javadoc contains the following text:
Note that while the comment separators /** and /* must be present, the leading asterisks on the interme‐
       diate lines can be omitted.

It's round about 280 on my syste, I don't that if the line number is fixed across systems. It's in the sectoin "Package Comment Files".

Anyway, the "/*" in that sentence should probably be "*/".