This code is a simple export of the LISP-style tree produced by ParseTree.toStringTree method. First you have to install the ANTLR4 according to this instructions. This solution is accompanied by a stackoverflow question where we discuss possible solution for the ParseTree XML export. Feel free to contribute to it if you have a better solution for the problem.
Once you have antlr4 ready (and reference in the CLASSPATH as well) you may use the following commands to run it:
antlr4 -visitor str.g4
javac *.java
java main < test_file.in
Test file has to contain an input in the LISP-style tree format and the result is XML on the standard output.