Chances are very good the Java that came with your computer is out of date and may well be only the Java Runtime Environment (JRE). Download and install a newer version of the Java JDK (Java Development Kit). You must install the JDK -- which includes the javac compiler for compiling Java code -- not just the JRE. In fact, the JDK includes a JRE in its directory structure and installs it in the main Java directory (see the screen capture at right).
On the Oracle website linked above, select the Java (JDK) SE 7u1. The "SE" stands for "Standard Edition"; the "JDK" stands for "Java Development Kit".
After the download completes, accept the defaults and install it. The installer exe will know where it needs to be on your hard drive -- just accept the location when the window pops up. The examples and screen captures assume the 64 bit version. The screen captures reflect whats current on 12/1/2011. Newer versions will have different update numbers (i.e., 7u2 instead of 7u1).