If you do not know if your computer supports the Java 2 Platform, you can open a terminal window, and type the command "java -version".
If the computer returns a message like:
java version "1.x.x" ...
then your computer supports the Java. If your computer do not support Java, then you must download and install the Java from Sun Microsystems. You can download java at Java SE Downloads.
End-users need to download the Java Runtime Environment (JRE) to run Java. Programmers need to install the JDK. JRE is included in the JDK. Programmers may also need NetBeans IDE. It is possible to download JDK with NetBeans, or download the packages separately.