Selvas,
To compile a Java program you need to install the JDK. This can be downloaded from
http://java.sun.com/docs/index.html.
When you install the JDK, you get the compiler and the Java Runtime environment which is required to actually run a program.
Hope that helps.
Jane
Ps ... I'm moving this to the Java Beginner discussion as it does not really involve Mock Exam errors.