Groovy is an agile, dynamic language for the JVM which combines many features from languages like Python, Ruby, and Smalltalk and makes them available to Java developers using a Java-like syntax. It is designed to help get things done on the Java platform in a quicker, more concise, and fun way. It can be used as an alternative compiler to javac to generate standard Java bytecode to be used by any Java project or it can be used dynamically as an alternative language, such as for scripting Java objects, templating, or writing unit test cases.
JCPP is a complete, compliant, standalone, pure Java implementation of the C preprocessor. It is intended to be of use to people writing C-style compilers in Java using tools like sablecc, antlr, JLex, CUP, and so forth. It has been used to successfully preprocess much of the source code of the GNU C library.
SuperWaba is a VM for PDAs. Because of the way it was written, you can use Java to develop programs for it. It supports exceptions, threads, many user interface controls, double and long 64-bit types, grayscale, color, 3D controls, and JNI and Java libraries, among other features. The project has been superseded and replaced with TotalCross.
FrAid (Fr[actal] Aid) is a programming language that is appropriate for mathematical computations, visualization, batch processing, and more. It features both a standalone application that provides a programming environment for the language and a system for integrating the language with Java. The Java interface allows mathematical equations and formulas to be used with Java code, making it easier to process numerical computations, symbolic computations, imaging, CAD, and more.
The Runabout is an extension of the Java libraries that adds two-argument multi-dispatch to Java without changing the language or the VM. It uses reflection to find visit methods, which are invoked using dynamically generated and loaded code. The Runabout does not need a special compiler or changes to Java's syntax. Dispatch with the Runabout is fairly fast, typically a factor of two to ten times slower than double dispatch. The Runabout is useful since it can help to make code faster and more readable. For example, a sequence of instanceof tests is a clear sign that a Runabout should be used instead.
The Karmasphere DP language is a high-performance non-blocking parallel language for performing data processing. It is designed to give the user a high degree of control over the usage of system resources, such as how many CPU cores or how much disk I/O time to use, without requiring the software developer to explicitly consider these issues in code. The implementation is a stand-alone library that can be used in any Java 1.5 environment. It can take full advantage of multiprocessor (SMP or NUMA) systems, and may be scaled sideways: since the interpreter and environment are stateless, an entire cluster of machines may run the interpreter in parallel without any need for synchronization.
MaVerick is a MultiValue database management system. MultiValue databases are said to be one of the computer industry's best kept secrets. First appearing over 30 years ago as PICK, they have continued to evolve through various commercial vendors, and are still in active development today. They are very resource friendly, are incredibly fast, feature a very user friendly data retrieval and reporting language (variously called ACCESS or English), and a rapid application development language based originally on Dartmouth Basic. The MaVerick project is an attempt to create an open source variant, written in Java.
joeq is a Java 2 (JDK 1.3 and 1.4) compatible virtual machine. It is unique in that it is entirely implemented in Java, leading to greater reliability, portability, maintainability, and efficiency. It is also language-independent, so code from any supported language can be seamlessly compiled, linked, and executed dynamically.