usage:

java <Java-options> -jar josm.jar <options> ...

options:

--help|-?|-h                              Show this help
--geometry=widthxheight(+|-)x(+|-)y       Standard unix geometry argument
[--download=]minlat,minlon,maxlat,maxlon  Download the bounding box
[--download=]<url>                        Download the location at the url (with lat=x&lon=y&zoom=z)
[--download=]<filename>                   Open file (any file type that can be opened with File/Open)
--downloadgps=minlat,minlon,maxlat,maxlon Download the bounding box as raw gps
--downloadgps=<url>                       Download the location at the url (with lat=x&lon=y&zoom=z) as raw gps
--selection=<searchstring>                Select with the given search
--[no-]maximize                           Launch in maximized mode
--reset-preferences                       Reset the preferences to default
--language=<language>                     Set the language

options provided as Java system properties

-Djosm.home=/PATH/TO/JOSM/FOLDER/         Change the folder for all user settings

For some tasks, JOSM needs a lot of memory. It can be necessary to add the following Java option to specify the maximum size of allocated memory in megabytes, on the other hand on slow systems, you can get JOSM to run stable through restricting the memory use:

-Xmx...m                                  Set maximum Java heap size in megabyte

examples

java -jar josm.jar track1.gpx track2.gpx london.osm
java -jar josm.jar http://www.openstreetmap.org/index.html?lat=43.2&lon=11.1&zoom=13
java -jar josm.jar london.osm --selection=http://www.ostertag.name/osm/OSM_errors_node-duplicate.xml
java -jar josm.jar 43.2,11.1,43.4,11.4
java -Djosm.home=/home/user/.josm_dev -jar josm.jar
java -Xmx400m -jar josm.jar

Parameters --download, --downloadgps and --selection are processed in this order. Make sure you load some data if you use --selection.