I have a Java app which needs to perform partial least squares regression. It would appear there are no Java implementations of PLSR out there. Weka might have had something
There has been work by Duncan Temple Lang: http://rss.acs.unt.edu/Rdoc/library/SJava/Docs/RFromJava.pdf .
My guess as to the most robust solution would be JGR. The developers of JGR have a mailing list, Stats-Rosuda and the mailing list Archive indicates the list remains active as of 2013.
There is also code that has been put up at Googlecode, with an example here: http://stdioe.blogspot.com/2011/07/rcaller-20-calling-r-from-java.html