Adit
Adit is another database interface tool built with Java.
Adit is meant to be a lightweight tool for querying a database.Some of the current features include: Connect to any database with a JDBC driver; Save query results to a delimited file; Save and restore SQL statements to disk;
View tables and field definitions; Get information (properties) about a query.

DataBase Java Console
DBJC is a program written in Java to query a database. It reads from a properties file, the connection parameters, and queries configured. Params can be read from stdin to execute a query more than once.

DbmJui
DbmJui is an attempt to clone DBMGUI, the database manager for MaxDB (formerly known as SAP DB). DBMGUI is written in VB so it can only run on Windows platforms. DbmJui uses the Java programming language. It can run on every platform where a JVM is available.

FreeQueryBuilder
FreeQueryBuilder is a GUI SQL client written in 100% Java.
With FreeQueryBuilder, you can create SQL queries without
directly writing SQL.

GUAM
GUAM is, as the name implies, a GUI frontend to allow easy administration of MySQL users. It is written in Java and uses the Swing toolkit. Since it is a pure Java application, it is completely cross-platform and should work on any platform that has a full Java implementation (and maybe even some of the cut-down implementations). GUAM is released under the GNU General Public License (GPL).

iSQL-Viewer
iSQL-Viewer is an open-source JDBC 2.x compliant database front end written in Java. It implements across multiple platforms features of the JDBC API. It does everything through a single interface. iSQL-Viewer works with most database platforms, including PostgreSQL, MySQL, Oracle, and Informix. iSQL-Viewer provides a variety of tools and features to carry out common database tasks.

PKLite SQL Client
PKLite is a Lightweight SQL querying tool written in Java. Connects to any JDBC compliant database and will run on any OS with a Java VM. Features: keyword highlighting, result formatting, statement history, multi-window, multiple databases connects at one time.

QueryForm
QueryForm is a robust Java application that provides a powerful GUI front end for JDBC-enabled databases. It creates forms on-the-fly through which you can query tables and browse the results with just a few keystrokes or mouse clicks. It also lets you insert, update and delete table rows without typing any SQL statements.

SQL Admin
SQL Admin is a Java client application to connect and send queries to different databases through JDBC. The main idea is to create a multiplatform and multidatabase thin client. For example you can connect to an Microsoft SQL Server from a Linux machine, or connect to a PostgreSQL/Linux server from a windows machine using the same application.

SQLMinus
SQLMinus is an SQL Client with many developer-friendly features including: auto-linking across tables; dependency discovery; simple, intuitive and powerful keys to sort columns and filter data; tab-completion of table and column names; etc.