An Experiment in Automatic Conversion of Legacy Java Programs to C#

Source-to-source transformation is an important tool for migrating key legacy programs to modern languages and platforms and giving them new life. Many organizations cannot do without their legacy systems on the one hand, but are stuck in an old technology on the other hand. Converting to a newer programming language can ease integration with modern technologies, give access to a wider developers population and/or lower maintenance costs. Serious language conversion efforts use automated tools, since manual conversion is out of question for non- trivial programs. We present our experiment in building a Java to C# transformer, Java2C#, that partially converts legacy Java code (version 1.1 or earlier) to C#. Java2C# is written in TXL, a language specially designed for program transformation, using tree re-writing. We explore and discuss the challenges and issues to consider when automatically transforming Java to C# and when building automated language transformers in general.