I just completed the port to Java 1.8 of Johan Idstam’s SIE parser for .NET (https://github.com/idstam/jsisie) and relased version 1.0 on Sonatype. Soure code and issue tracking is available here: https://github.com/perNyfelt/SIEParser. The released artifacts are available on Maven Central at http://search.maven.org/#artifactdetails%7Ccom.github.pernyfelt.sieparser%7CSieParser%7C1.0%7Cjar
This library (released under MIT license) can read an write SIE Accounting files of all types (1-4). I am using it in various financial products that I am working on as well as in my work as a consultant in financial systems in Sweden. Hopefully you will find it useful too!