Thinlet is a GUI toolkit, a single Java class, parses the hierarchy and properties of the GUI, handles user interaction, and calls business logic. Separates the graphic presentation (described in an XML file) and the application methods (written as Java code).
Its compressed size is 28KB, and it is LGPL licensed.
Thinlet runs with Java 1.1 (browsers' default JVM) to 1.4, Personal Java, Personal (Basis) Profile, and MIDP. Swing isn't required.