SimpleDBM is a multi-threaded transactional database engine. It has a very small footprint and can be embedded in the address space of an application, or used in network client server mode. It provides a simple programming API that can be learned very quickly. SimpleDBM supports ACID transactions, steal/no-force buffer management, lock-based concurrency, row level locks, b-tree indexes, tables, write ahead log, crash recovery, and deadlock detection.
Zynaptic Reaction is a flexible asynchronous programming framework for Java which may be used to implement complex event-driven applications. It is heavily influenced by the Twisted programming framework developed by TwistedMatrix Labs for the Python programming language. The focus of the Reaction library is on the concurrency and callback model and as such it is application neutral. It can be used to manage lots of concurrent I/O or to farm out compute intensive tasks to multicore processors. As well as being usable as a basic Java library, Reaction can also run as an independent OSGi service and integrate into any GUI framework you choose.
The Java Engine for Testing (JET) is a system for running distributed automated tests. It has been used by Sun for testing the High Availability DataBase (HADB), JavaDB, PostgreSQL, Memcached, and the MySQL Cluster Manager. JET should be a good way to write your tests if the product you want to test is distributed or has a client/server architecture, if it is natural for you to write the tests in Java, and if you want to invest time in developing tests and abstractions for later reuse.
CODERU is a Java code quality tool to enforce design quality in respect to packages (and therefore modules) dependencies. The Java language is lacking a module concept. CODERU is an approach to close the gap. The approach relies on reserved package names, and the allowed dependency rules between them are expressed in a general way. It includes a Maven plugin for checking your code for rule conformance.
CompactBeans is a separated-out implementation of the java.beans.Introspector and associated Descriptor classes, targeted at Java 1.8SE Compact Profile 1. The code is based on the openjdk source bundles. The aim is for API compatibility as much as possible. In the simplest case, a package import rename is all that is required.