BeanShell is dynamically interpreted Java – or better: BeanShell is a small, free, embeddable, Java source interpreter with object scripting language features, written in Java. You can use BeanShell interactively for Java experimentation and debugging or as a simple scripting engine for your applications.

Some features:

• Uses the Java reflection API to provide runtime interpreted execution of Java statements and expressions.
• Transparent access to all Java objects and APIs.
• Covers the full Java statements and expressions syntax
• Emulation of strongly typed variables and methods
• Primitive value handling with correct numeric promotion
• Full Java arithmetic, logical, and bitwise operations
• Object construction and handling including multi-dimensional arrays
• Loops and control structures with breaks and returns
• Method invocations with polymorphic/overloaded method resolution
• Full exception handling
• BeanShell scripts can be used to implement arbitrary Java interfaces (requires JDK1.3+)

• Dynamically typed (un-typed) variables

This tech is of course a little bit older than other announced ones – but if you are one of those who missed articles like the Java Developer Journal from summer 2000, you might find it worthful to take a look…