Amin Ahmad has released Ropes for Java 1.2.0, an open source (GPL) implementation of the rope data structure in Java. "A rope is a high performance replacement for Strings. The datastructure, described in detail in "Ropes: an Alternative to Strings", provides asymptotically better performance than both String and StringBuffer for common string modifications like prepend, append, delete, and insert. Like Strings, ropes are immutable and therefore well-suited for use in multi-threaded programming."