Squirrel SQL is a very good Java based SQL client. This tool uses JDBC to connect to any database. The only requirement: A JDBC driver must be present.
Squirrel is open source and is at SourceForge hosted. Life into the project was launched by Colin Bell, I think it was in 2001. In any case, says the copyright of the entry in the class: Main.java.
A few years later, Gerd Wagner then intervened into the action. Colin and Gerd are still the project admins at SourceForge. The operation and performance are great and the possibilities are very extensive. Could be noticed at work that the squirrels attack a few years and convinced by a good many small features. Now is the end of the adulation 
Unfortunately, the UI could not keep pace with progress. It seems a bit in the years come:
But it's open source. So do not complain: tackling! No sooner said than done. To avoid reinventing the wheel, I've fallen in NetBeans. Specifically, on the NetBeans platform . Here is an excerpt of the description from Wikipedia:
The NetBeans Platform is an application runtime - a basis for a generic large desktop application. Most applications have similar requirements: menus, document management, change settings and so on. The NetBeans platform created for example, menus or generates code for saving settings. The developer must use his code as a NetBeans module, create and add this to the platform to create a platform-independent application. The NetBeans platform is designed to allow developers to concentrate on the business logic as essential tasks, saving time and effort.
More details get updated very often here .
Squirrel uses already currently a small part of the NetBeans platform. The SQL editor is based on the NetBeans editor. It provides SQL code completion and automatic syntax checking. It has useful shortcuts for bookmarks with Ctrl-Space, dissolve the IntelliSense function (auto-completion of SQL commands).
My first try with port-Squirrel and Netbeans can see in the pictures below:
To achieve this state intervention in many places in Squirrel's source code were necessary. Unfortunately, often working directly with JInternalFrames, which prevented a lean adjustments by a few refactorings. Rocketed to the current state I can tell the size of the package "Squirrel" in the considerable height.
Because of the great effort I am of NetBeans this way is no longer quite so sure. The cost \ benefit is not in a good relationship. Only when more features of the NetBeans platform would be used, it would look better again. NetBeans has a fine example module system, an auto-update Mechnismuss, shortcut management, and more. Squirrel could offer a complete port on the NetBeans Platform hightlighting example syntax for XML. Even the well-known problem with very large SQL statements in SQL Editor would be solved. However, this adaptation is still an unknown quantity for me. The Squirrel's editor based on the NetBeans editor already, but this is a very old version. Especially since NetBeans 6.0 has been in use \ integration of the editor, did some (project Schliemann)
But, I'm starting to polish the front end of the mission. So back on topic: I will go and follow the NetBeans way but not looking for an alternative.
to miss the squirrel a fresh UI 
Those interested in the sources, can report you!