BeanShell is a small, free, embeddable, Java source interpreter with object scripting language features, written in Java. BeanShell executes standard Java statements and expressions, in addition to obvious scripting commands and syntax. BeanShell supports scripted objects as simple method closures like those in Perl and JavaScript(tm).

You can use BeanShell interactively for Java experimentation and debugging or as a simple scripting engine for you applications. In short: BeanShell is a dynamically interpreted Java, plus some useful stuff.