is not moving ahead after fetching 2.14B records out of 2.5B records and exists out after long time

I am fetching records from Oracle 12c using JDBC driver. I have total 2.5B records, after successful fetching 2.14B records (2147483000), got stuck and not moving ahead and exists out after a long time. I am fetching this data from a simple Hash partitioned table having 2000+ child partitions having a single NUMBER data typed column. Also, I do have sufficient memory on my machine.

suggestions/ideas anyone?