Please check previous paragraphs for details on how to choose the JDK to install.

Linux Windows
Make sure the bin/ directory of the JVM installation is added to PATH variable of the operating system so the application could be executed by using java command in a terminal window: the PATH for the user should be set to include the directory containing the command line executables (e.g. java or javac) of this installation. In Linux this would be the bin/ directory of the Java installation. In other words, this should be the default installation for any shell or command prompt from which the FWD technology will be built or used.

To install OpenJDK 1.8, following commands can be used:

sudo apt-get install openjdk-8-jdk openjdk-8-source
cd /usr/lib/jvm
sudo rm default-java
sudo ln -s java-8-openjdk-amd64 default-java

It is also recommended to set the user's CLASSPATH to current folder (“.”):
export CLASSPATH=.
Please note that this will only set the variable for the current terminal session. You will need to set this each time your start a new terminal session, if it is needed.

The Oracle JDK 1.8 is a well tested option for Windows. The JDK can be downloaded from

If you are planning to build FWD binaries on Windows make sure to install the accompanying JRE when installing the JDK, this is the default option of the JDK's installer.

Make sure JAVA_HOME system variable exists and points to the location of the installed JDK. The variable is needed by the FWD build scripts to locate the Java build files. If not defined explicitly it would point to the location of the public JRE installed together with the JDK (or any other JRE set as the default one), which is missing the build files, and the build would fail.

Add %JAVA_HOME%/jre/bin/server to the system PATH variable. This ensures that the FWD client spawner process, spawn.exe, locates jvm.dll correctly.

Because of a bug in how the gcc C++ compiler processes paths (please see #3273 for further information), this value cannot contain spaces!

There two possible approaches to avoid this depending on the current system configuration:

1. System with no JDK yet installed. Install JDK into directory without spaces, like C:\jdk180 for example.
2. System with JDK already installed into something like "Program Files\path to JDK" containing spaces and there are the reasons to keep this configuration. in this case create symbolic link to JDK that has no spaces inside:
mklink /D SomePathWithNoSpaces "The target path\to JDK with\spaces inside" 

an example (having C:\ as current directory):
mklink /D jdk180 "Program Files\Java\jdk1.8.0_121" 

The quotation in link creation command is mandatory for mklink to properly resolve the original directory. After link has been created it must be used in JAVA_HOME and JRE_HOME environment variables instead of original path with spaces.

As alternative solution to avoid that, use the legacy 8.3 filenames for tokens that contain spaces. In a default Java installation, they are Program Files or Program Files (x86) must be replaced with PROGRA~1 and PROGRA~2 respectively, but they can differ if Windows was reinstalled. Use dir C:\ /X to see actual legacy name for each file/dir, in second to the last column. The value of this environment variable for default installation will look like this:

The above listed environment variables must be defined system wide so that they are available to all users. On Windows 7, you can access Environment Variables... in Control Panel/System and Security/System/Advanced System Settings, Advanced tab.