Java Runtime Environment/How to run java applications

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Many Java applications come packaged as a file with the ".jar" extension

Double-click a jar

Many jar files are "runnable". This means you can simply double-click the file on many operating systems. The file contains details of which Java class files to run by default, and the application just starts up. Easy!

This assumes a few things though. Firstly you'll need Java installed as detailed above, and with the necessary operating system hooks enabled, and these may not be available for some operating systems.

This is also an security issue. Think twice before you set up your system to start jar files automatically by just clicking – this would work with all downloaded jar files then (also with accidental, malicious downloads)! Better use the command line or a manually built link/script.

Run it on a command terminal

This way is a more basic fundamental approach which you can use on any operating system. Some Java applications (for example, mkgmap.jar) cannot run without terminals.

It's not so hard even if you don't have any experience of command lines. For example for to run JOSM, type commands like this:

cd path_to_the_directory_that_JOSM_is_installed_in
java -jar josm.jar

then the JOSM runs.

You can add options on the command line. There are two kinds of options. One kind for initialising the Java Virtual Machine, the other for application options.

java [Options for JavaVM] -jar application.jar [Options for the application]

The following are commonly used options for the Java VM.

memory options
  • -Xmx is the only memory option which really matters. This is the maximum memory capacity of the Java application. The default value is 64 MB which is often too small. Increase it to, for example, 512 MB with the option "-Xmx512m". (other java memory options)
proxy options
  • -Dhttp.proxyHost= specifies a proxy server if you want to use http though a proxy server. For example, "-Dhttp.proxyHost=".
  • -Dhttp.proxyPort= specifies a proxy port. The default value is 80. For example, "-Dhttp.proxyHost=8080".
  • -Dhttp.proxyUser= specifies proxy user name. Set it if the proxy server requires authentication.
  • -Dhttp.proxyPassword= specifies proxy password. Set it if the proxy server requires authentication.
  • Specify it, if you need IPv6. By the way, the OpenStreetMap-server doesn't support ipv6 yet.
graphic accelerations
  • -Dsun.java2d.opengl=true Enabling OpenGL. Specify it if you know your PC has OpenGL 2D graphic accelerators. If you have problem with this setting (false icon and background, dialog. tested on WinXP + nVidia FX1500 + dual monitor) use:-Dsun.java2d.opengl=true -Dsun.java2d.opengl.fbobject=false although note that the opengl option can cause problems with window managers on Linux.
  • -Dsun.java2d.d3d=true -Dsun.java2d.ddscale=true Enabling DirectX graphic acceleration for Windows.

The options for the application depend on each applications. See their page for these.

Where is the command terminal?

  • Windows:
    • Click the "start" button. You can find "Command Prompt" in "Programs/Accessories". If you don't find it, you may be missing this shortcut, however you don't need it...
    • Click the "start" button then click "Run..." and enter "cmd" in a box on the Run window.
    • Alternatively create a file 'run-josm.bat', and edit it in notepad. Enter your command as the only contents of the file. Save it, then double-click the file to run it. If the black command window disappears immediately, you can debug by adding a new line 'PAUSE' in the bat file.
  • Mac OS X: Go to "Applications" and then "Utilities" in Finder. You will find "Terminal".


Usually, the JRE installer registers the .jar file type to be run by javaw.exe (which is another java running command. It is special for Windows to run Java GUI applications without terminals.) command. So you can run .jar just by doble-clicking it. However, this way cannot add options. To add options, you can choice from two ways.

  • Making a .bat file.
    1. Open a text editor (for example, notepad) and create a new file by it.
    2. Write commands on it. I recommend to write a "cd" command before "java" command to specify the default running directory.
    3. Save it as .bat file (for example, josm.bat).
    • When you double-click the .bat file, a command terminal opens and do the commands on the .bat file.
  • Making a shortcut. (.lnk file)
    1. Right-click on a .jar file. Click "Create Shortcut" on the pop-up menu. (You can use "Send to/Desktop (create shortcut)", too.)
    2. Right-click the created shortcut and select properties.
    3. The full path of .jar file is shown on Target box. Add "javaw [Options for JavaVM] -jar " before the .jar path. Add " [Options for the application]" after the path.
    4. If you need to specify the current directory when it runs, you can write it in "start in" box.
    • When you double-click the shortcut, it runs the application with the options.
    • The shortcut is free to move, to rename and to change the icon. I recommend it to rename it to the application name (eg. "JOSM" without "shortcut to"), and to move it to under the "start menu".

Mac OS X

You need Mac OS 10.4 or better. 10.3 will not do the job. In 10.4.x and 10.5.x, simply double click on the jar file and Java 1.5 should load the .jar file. If you need to allocate more memory (in order to edit larger files or you get the 'strange things may happen' memory error),

  1. Go to Applications and then Utilities in Finder.
  2. Open Terminal
  3. Change to the directory where josm-latest.jar is... If it's on your desktop, try 'cd Desktop'
  4. Copy and paste the following line in to the terminal to start JOSM with more memory:
java -Xmx512M -jar josm-latest.jar

Include -Dapple.laf.useScreenMenuBar=true to place the menu on the OS X menu bar, and -Xdock:name="JOSM" -Xdock:icon="logo.png" to give it icon and name.

If you're not familiar with scripts just use the Jar Bundler application, coming with MacOS X. It'll create a start application, let's call it "JOSM!". You'll find it here /Developer/Applications/Java Tools/ or here /Developer/Applications/Utilities/. Just double click to launch it. In the first menu build information enter the location of the just downloaded JOSM jar file by clicking the choose... button. In the third menu properties choose the edit box vm options to enter the appropriate memory settings. If you're able to afford it try spending up to a GB RAM to JOSM. Here's what to enter into the edit box: -Xmx512M -XX:MaxPermSize=512M (which starts the JOSM application with 512MB and grants up to 1GB of RAM). Then press create application... to create the start application (call it JOSM!, f.e.). JOSM! does not have to be in the same directory as the jar file. Just save or move JOSM! to your applications folder. Double click JOSM! to start the JOSM aplication.

via shell scripts

Input a command line as the above is the basic. Usually the command line become long. It is better to make a shell script to run for each jars. There are some users make some useful shell scripts.

You can use a shell-script developed by User:Cobra to keep JOSM always up-to-date, start it, and pass files to it.

Or you can use the following simple script to use always the latest Josm Version:

export JAVA_HOME=/usr/local/java/jdk1.6.0_04/
DCOPREF=`kdialog --title "Hole JOSM"  --progressbar "Hole JosmLatest" 100`
wget -N
dcop "$DCOPREF"  close
$JAVA_HOME/bin/java -Xmx1024M -DproxyHost=$PROXY -DproxyPort=8080 -jar josm-latest.jar