Well it seams to be a EBCDIC data file, the fields of data unreadable should be packed numeric data, so "dd" will do the trick, transfer the data file to Unix system and run "dd" with conv=ascii, to transfer all packed numeric to ascii data, you will need also the RPG data definition to known where the fields start and end, to them load ascii data correctly into your java application.
Regards,
Carlos Almeida,