/usr/share/doc/default-jre-headless/api is in default-jdk-doc 0.52.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/default-jre-headless/../openjdk-7-doc/api
/usr/share/doc/default-jre-headless/../openjdk-7-doc/api