SQuirreL SQL Client is a popular open source graphical application written in java that allows users to browse tables and issue all kinds of SQL commands. SQuirrel can be used in variety of OS like Java application since it is written in java. The newer and recent version i.e. 3.6 supports Java 1.6 or higher. If you are running older version of java, you should use the older SQuirrel versions. Each database has its own application/tool to access its database. SQuirrel SQL Client is the answer for those people who can use all the database in one application. I believe SQuirrel SQL Client is the best open source application I can find in the market to access any database in one application. Here are the few tips to set up best application to connect to PostgreSQL database.

1.  Download SQuirrel SQL Client from http://squirrel-sql.sourceforge.net/#installation
2.  Go to postgreSQL website and download the right driver depending on your database
3.  Launch the SQuirrel SQL Client.
4.  Open Driver list from left menu, click the plus sign “Create a New Driver”.
5.  Type ” Greenplum Driver” or your choice of name in “Name” text box.
6.  Type jdbc:postgresql://:/ in “Example URL” text box. Port number might get changed for you.
7.  5. Type org.postgresql.Driver in “Class Name” editable drop down list.
8.  Click “Extra Class Path” tab.
9.  7. Click “Add” and select the JDBC jar for postgresql postgresql-9.4-1201.jdbc41.jar.
10.  Click Ok, and we are done defining the driver.

At the end, now create an alias for the DB using previous driver and providing URL, username, & password.