"JoSQL (SQL for Java Objects) provides the ability for a developer to apply a SQL statement to a collection of Java Objects. JoSQL provides the ability to search, order and group ANY Java objects and should be applied when you want to perform SQL-like queries on a collection of Java Objects."
For example, to find all the HTML files that have been modified in December 2004:
SELECT * FROM java.io.File WHERE name $LIKE "%.html" AND lastModified BETWEEN toDate('01-12-2004') AND toDate('31-12-2004')
via o'reilly's code zoo.