Apply cosmetic changes to String.java from OpenJDK 8u121-b13

Upstream updated a year in a copyright and removed some unhelpful
'@throw NullPointerException' javadocs, and those changes were omitted
here. This change applies those changes. It also removes a few
spurious whitespace diffs that crept in along the way.

Test: make checkbuild
Change-Id: Id8520daaa2dd67d02818fe2bb52994f7e859fbdf
1 file changed