This is a FAQ. You can put //NOSONAR
on the line triggering the warning. I prefer using the FindBugs mechanism though, which consists in adding the @SuppressFBWarnings annotation:
@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(
value = "NAME_OF_THE_FINDBUGS_RULE_TO_IGNORE",
justification = "Why you choose to ignore it")