Walkabout Revisited: The Runabout

We present a variation of the visitor pattern which allows programmers to write visitor-like code in a concise way. The Runabout is a library extension that adds a limited form of multi-dispatch to Java. While the Runabout is not as expressive as a general multiple dispatching facility, the Runabout can be significantly faster than existing implementations of multiple dispatch for Java, such as MultiJava. Unlike MultiJava, the Runabout does not require changes to the syntax and the compiler.In this paper we illustrate how to use the Runabout, detail its implementation and provide benchmarks comparing its performance with other approaches.