In order to use the OT, it should only be necessary that the computer in question has Java installed. Most computers have Java pre-installed, but if this is not the case, the latest version of Java (also known as the Java Runtime Environment or JRE) should be downloaded from http://java.com/. Regarding the version of Java, it is absolutely essential that Java 7 be installed, although Java 8 probably works okay. The currently installed version can be checked by typing java -version on the command line, the output of which should look something like this:
java version "1.7.0_71" Java(TM) SE Runtime Environment (build 1.7.0_71-b14) Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)The number that follows the underscore refers to which update of the Java version has been installed. Updates appear regularly and should always be installed. When reporting a problem with the OT, the full version number including the update should be reported.
OpenJDK versions of Java such as IcedTea that are common on many modern Linux installations have proved problematic in the past and thus we recommend that the official release from Oracle be used wherever possible.