java: loss of precission

Change-Id: I0563a76b1d2c838e6301bf7a9ed154c77a98c0d9
Reviewed-on: https://gerrit.libreoffice.org/12000
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>