PostgreSQL: Save roundtrips / Network performance
there is nothing on PostgreSQL side to deal with this.  

JDBC side i know nothing about but quick google search points to no

A solution i use when working with large data sets is to fetch only a few records at a time  1000 to 10000.

Select * from tablename where tablename.id &gt; 1 ordered by id limit 1000


next set of queries 

Select * from tablename where tablename.id &gt; 1000 ordered by id limit 1000


Some people call this  asynchronous  fetching/paging.  

Some background
Most db connections run in synchronize mode by default, "command sent"  client waits until all data is delivered.  This makes the app appear to hang for long periods of time, this makes the users think the app has crashed or something else has gone wrong. 

Using asynchronous technique the data is continuously fetch and  delivered using a background process/thread while the rest of the code is free to continue working giving the user the appearance the application is very snappy.

Its allot harder to write code around fetching only a few records at a time but can be  worth it on big data sets, as the app does not have to wait on all the data

There are several tools to make this easier,  such as creating cursor on the server and fetch only X records from the server. But there are draw backs to cursors,  eating server resources,  required to run clean up code.

Some client libraries makes this easy by directly supporting cursor other do not support this feature  JDBC does not appear to support this so it will have to be written.