title: compile .java through command prompt
body: <p>I'm new in programming, I'm learning Java right now. I tried to use the <em>javac</em> command, but the environment says that <em>javac</em> is an unknown command. </p>
  
  <p>How to use "javac" to compile .java files from the command prompt? I'm using eclipse 1.2.2.20100216-1730, JRE 1.6 and JRE6</p>