I am trying to install PMD plugin but I can not.

I used the update site "
https://sourceforge.net/projects/pmd/files/pmd-eclipse/update-site/"
according to the guidelines of "http://pmd.sourceforge.net/eclipse/".

I'm using Eclipse Luna (4.4.2).

The error that occurs in Eclipse is:

Unable to read repository at
https://sourceforge.net/projects/pmd/files/pmd-eclipse/update-site/.
Unable to read repository at
https://sourceforge.net/projects/pmd/files/pmd-eclipse/update-site/.
https://sourceforge.net/projects/pmd/files/pmd-eclipse/update-site/ is not
a valid repository location.

Attached the error screen.

Thank you in advance for your help!