Java Interface for postgres database

Hi

I am trying to build a java front end to my postgres database. I have the database, psql and jdbc setup correctly and have made various tables but I need to make a front end for data input and retreival.

I am thinking of having a java program that asks a series of questions and inputs the details into the correct part of the DB and once finished sends back an integer depending on the values input to the java program.

The problem is that I don't know how to use sql commands within a java program and how to send back values from the database to the java program. Does anyone know this?

Any help much appreciated

Regards