Not working with Java 11

[pstast]

Unfortunately this great tool stopped working after upgrading to OpenJDK 11, which is the only version in Debian Buster.

Position V:0.0 L:0.0 R:0.0
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.itextpdf.text.pdf.MappedRandomAccessFile$1 (file:/XXX/PortableSigner/lib/itextpdf-5.1.3.jar) to method java.nio.DirectByteBuffer.cleaner()
WARNING: Please consider reporting this to the maintainers of com.itextpdf.text.pdf.MappedRandomAccessFile$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release