Does the user really need all that data in the applet, at once?
If not, I'd consider putting a LIMIT or ROWNUM clause in your query to cut down the number of rows sent to the applet. Let the user query again for the next block of rows as s/he needs them.
If you do really need to send all of that data at once, then
you should try increasing the heap size in the JVM. Google on -Xms and -Xmx for more information.
If you're running
Tomcat on windows and you've installed the "start menu" items, you can alter the memory settings by going to Start -> Programs -> Apache Tomcat -> Configure Tomcat -> click on the
Java or Memory tab.
There are fields for the initial and maximum memory settings.
You'll then have to deal with streaming all of that data over the network and then your user will have to deal with all of that data within the JVM under which the applet is running. If it's blowing up the server's JVM it'll probably cause you headaches on the client's JVM as well.