Granted I'm painting with broad brushstrokes here, but here are two job websites which amalgamate job listings from multiple other websites on the net. You can use them to do trend analysis. Here are graphs of the trends for the "java" keyword coupled with the "groovy" keyword in job listings.

[1]

http://www.indeed.com/jobtrends?q=groovy+java&relative=1 [2]

[3]

http://www.simplyhired.com/a/jobtrends/trend/q-groovy+java [4]

Enjoy,
Jason