Have you tried executing the query from the SQL Plus prompt.
See if it works.
If it does then do one thing, put the execution of query in Java and the statements in the java code that reterive the results in a try catch block that catches a generic exception (Exception).

It had happened to me once that I was just catching the SQLException in the catch block and runtime exception was thrown from the block and the program used to hang. I could never guess why.

See if this helps..

-Kaustubh.